1. An eye state detection apparatus, comprising: a camera unit configured for capturing an original image of a user's face; a storage unit configured for storing a program and the original image of the user's face; and a processing unit electrically connected with the camera unit and the storage unit, the processing unit configured to load and execute the program to receive the original image, obtain a face image from the original image, define each center point of two nostrils on the face image, compute a distance D between the two center points of the two nostrils and determine coordinates of an initial point A (x1, y1) representing a midpoint between the two center points of the two nostrils, determine coordinates of a reference point B (x2, y2) according to the distance D and the initial point A (x1, y1), define a rectangle on the face image according to the coordinates of the reference point B (x2, y2), and obtain an eye image of the user's eye from an area of the rectangle; wherein x2=x1+k1×D, y2=y1+k2×D, k1=1.6˜1.8, k2=1.6˜1.8, and the coordinates of the reference point B (x2, y2) represents a middle point of the rectangle.