Disclosed is a solid state detector which comprises a photo-conductive layer for generating charges upon irradiation of recording light and a substrate laminated to the photo-conductive layer, the substrate having a thermal expansion coefficient different from that of the photo-conductive layer. The solid state detector prevents deformation and breakdowns due to temperature changes of environments. Specifically, the solid state detector comprises a photo-conductive layer and a substrate laminated to the photo-conductive layer, the substrate having a thermal expansion coefficient smaller than that of the photo-conductive layer. In the solid state detector a deformation suppression layer, which has a thermal expansion coefficient smaller than that of the photo-conductive layer and suppresses deformation resulting from thermal expansion of the photo-conductive layer and the substrate, is laminated on a side of the photo-conductive layer opposite from the side of the substrate.