1. A method of producing an ultrasound image in an ultrasound diagnostic apparatus, comprising: with an ultrasound probe of the ultrasound diagnostic apparatus, performing transmission and reception of an ultrasonic beam toward a blood vessel in a subject based on an actuation signal and outputting a reception signal of the ultrasonic beam; with a transmission/reception circuit of the ultrasound diagnostic apparatus, producing the actuation signal and producing a sound ray signal obtained by processing the reception signal; with an image producing processor of the ultrasound diagnostic apparatus, producing an ultrasound image based on the sound ray signals; with a candidate vascular wall boundary point determining processor of the ultrasound diagnostic apparatus, determining candidate vascular wall boundary points in the ultrasound image based on the sound ray signal; with a first evaluation value calculating processor of the ultrasound diagnostic apparatus, calculating a first evaluation value representing accuracy of each of the determined candidate vascular wall boundary points as a vascular wall boundary point; with a second evaluation value calculating processor of the ultrasound diagnostic apparatus, by means of a sound ray signal in a predetermined depth range including the determined candidate vascular wall boundary points and a sound ray signal adjacent to the sound ray signal, calculating a second evaluation value representing similarity between the sound ray signal and the adjacent sound ray signal; with a third evaluation value calculating processor of the ultrasound diagnostic apparatus, calculating a third evaluation value for determining the vascular wall boundary point from among the candidate vascular wall boundary points based on the first evaluation value and the second evaluation value; and with a boundary determining processor of the ultrasound diagnostic apparatus, determining the vascular wall boundary point in the ultrasound image based on the third evaluation value and determining a vascular wall boundary based on the determined vascular wall boundary point; with an intima-media thickness calculating processor of the ultrasound diagnostic apparatus, calculating an intima-media thickness based on the determined vascular wall boundary point; and with a display controlling processor of the ultrasound diagnostic apparatus, displaying the ultrasound image of the blood vessel and the calculated intima-media thickness on a display, wherein the second evaluation value is calculated by the following second evaluation function C 2 (b i-1 (j),b i (j′)) using sound ray signals of a plurality of points above and below a candidate vascular wall boundary point including the candidate vascular wall boundary point in a depth direction and sound ray signals adjacent to the sound ray signals; ⁢ [ Equation ⁢ ⁢ 1 ] C ⁢ ⁢ 2 ⁢ ( b i - 1 ⁡ ( j ) , b i ⁡ ( j ′ ) ) = ∑ k = 0 WL - 1 ⁢ { f ⁡ [ i - 1 , j + k ] - ( ∑ k = 0 WL - 1 ⁢ f ⁡ [ i - 1 , j + k ] / WL ) } { f ⁡ [ i , j ′ + k ] - ( ∑ k = 0 WL - 1 ⁢ f ⁡ [ i , j ′ + k ] / WL ) } ∑ k = 0 WL - 1 ⁢ { f ⁡ [ i - 1 , j + k ] - ( ∑ k = 0 WL - 1 ⁢ f ⁡ [ i - 1 , j + k ] / WL ) } 2 ∑ k = 0 WL - 1 ⁢ { f ⁡ [ i , j ′ + k ] - ( ∑ k = 0 WL - 1 ⁢ f ⁡ [ i , j ′ + k ] / WL ) } 2 ; b i : a candidate vascular wall boundary position (depth) corresponding to the boundary of an intima-media complex of a sound ray L i , i: the position of a sound ray in a scan direction, j, j′: the depth direction positions of the candidate vascular wall boundary points, k: a search depth range, WL: a depth range in which similarity calculation (correlation calculation) is performed (the number of sampling points corresponding to about a wave train length of a transmission wave).