An optical stereolithographic apparatus performs optical stereolithography by preparing a mask on a light-transmissible member (31) on the basis of data for one layer with respect to optical stereolithography, exposing an unhardened resin layer (96) of photohardenable resin to light through the mask, and repeating an exposure operation. The optical stereolithographic apparatus has an optical system in which the light-transmissible member (31) and the unhardened resin layer (96) are spaced from each other at a predetermined distance, and the unhardened resin layer (96) of the photohardenable resin is subjected to a projection exposure through the mask.