For the purpose of providing an image projection method for incorporating all data values along a projection axis on a projection image produced from three-dimensional data, a pixel value G at a point of intersection of the projection axis and projection plane is determined as:.times..times..times..times..times..times..times..times. ##EQU00001## where the number of three-dimensional data values along the projection axis is denoted by n, a data value is denoted by Vi, and a real number greater than one is denoted by r.