An outer shape determination device includes: a mounting base having a rectangular mounting surface for placing an object to be subjected to determination thereon; a longitudinal light-emitting optical waveguide, a longitudinal light-receiving optical waveguide, a transverse light-emitting optical waveguide, and a transverse light-receiving optical waveguide which are provided along the periphery of the mounting surface; a heightwise light-emitting optical waveguide and a heightwise light-receiving optical waveguide which are erected upwardly from the mounting surface; a light source connected to light-emitting cores of the longitudinal, transverse and heightwise light-emitting optical waveguides; a photoelectric conversion element connected to light-receiving cores of the longitudinal, transverse and heightwise light-receiving optical waveguides; and an outer shape calculating means for receiving a light interception signal from the photoelectric conversion element to perform a computation process, thereby calculating the outer shape of the object.