A method for preparing an optical device by dicing includes applying a dicing tape onto the back face of a substrate provided thereon with a large number of optical elements on the surface thereof and dicing the substrate from the surface side of the substrate using a blade to thus prepare individual optical devices and the method is characterized in that the dicing operation is conducted in several stages using a blade which can ensure a moderate autogenously blade-generating effect. An optical device prepared by the method includes a substrate and an optical element formed on the surface of the substrate and it is characterized in that the maximum size of the ruptures present on the back face of the substrate in the direction vertical to the cut surface is not more than 0.1 mm.