It is provided that a reflection plate of semiconductor heat treatment, which is resistant to cracks or deformations by controlling the adsorption of foreign materials and the production of reaction. Said reflection plate 1 for semiconductor heat treatment is composed of a disk-shaped or ring-shaped plate of optically transmissible material and a plate 2 of inorganic material hermetically enclosed in said disk-shaped or ring-shaped plate, in which said plate of inorganic material has at least one side in contact with said plate of optically transmissible material, said at least one side 2a having a surface roughness of Ra 0.1 to 10.0 .mu.m, said at least one side 2a formed grooves 2c therein.