A heat radiating plate storage tray has a plate main body, and a plurality of first projection portions provided on a first surface of the plate main body. A heat radiating plate having a rectangular recessed portion on a surface thereof is capable of being mounted on the first surface of the plate main body, a top face of the first projection portion supports a bottom face of the recessed portion of the heat radiating plate, and a height of the first projection portion is larger than a depth of the recessed portion of the heat radiating plate.