An optical measurement apparatus includes a thermal insulation housing, a first light-transmissive plate, a second light-transmissive plate, a heat-conductive layer, a cooling source and a photosensor. The thermal insulation housing, the first light-transmissive plate and the second light-transmissive plate define a chamber. The heat-conductive layer is disposed in the chamber, the cooling source is coupled to the heat-conductive layer, and the photosensor is disposed outside the chamber and on one side of the second light-transmissive plate facing away from the first light-transmissive plate.