A holographic ROM system of the present invention includes a holographic disk for storing information in a form of hologram; a pick-up module for optically reading the information stored in the holographic disk and producing an electrical signal in response to what has been read; and a control unit. The pick-up module has at least two light sources which are controlled by the control unit and a temperature measuring device for measuring an operating temperature of said at least two light sources, and the temperature measuring device transmits a temperature signal indicating the operating temperature to the control unit.