1. A method of measuring three dimensional shape, the method comprising: irradiating light onto a substrate having a measurement target formed thereon to capture an image by receiving light reflected by the substrate; setting up an object region in which the measurement target is disposed and a ground region corresponding to a remaining region in an inspection region of the image; irradiating a grating patterned light onto the substrate having the measurement target formed thereon to capture a patterned image by receiving the grating patterned light reflected by the substrate; and obtaining height of each position in the inspection region by using the patterned image to establish a ground height with respect to the measurement target with a height of the ground region.