1. An apparatus for reconstructing 3D images by using magnetic resonance imaging (MRI), comprising: an image acquiring unit configured to acquire a plurality of magnetic resonance (MR) images about a region of interest of an object at different angles, respectively, wherein the region of interest is defined by an x-y plane, which is a flat surface of the region of interest, and a z-plane, which is a slab of the region of interest; an image reconstructing unit configure to reconstruct the 3D image by using the plurality of MR images, wherein the plurality of MR images include information of a slice direction about the region of interest, which is changed depending on the different angles; and a pulse sequence controlling unit configured to add angle decision gradient having different amplitudes to slice selection gradient that decides a change of a magnetic field in the region of interest along the z-direction in order to acquire the plurality of MR images at the different angles, wherein the angle decision gradients are determined by using a frequency encoding gradient for deciding a change of a magnetic field in the region of interest along an x-direction and the acquisition angles of the MR images and wherein the angle decision gradients are expressed by the following equation; 
 G SS — add i =G RO ·tan θ i , wherein G SS — add i is an ith angle decision gradient, G RO is the frequency encoding gradient, θ i and is the acquisition angle of an ith acquired MR image.