A semiconductor chip on which a light receiving element is mounted, a preamplifier for amplifying an output signal from the light receiving element, and an insulating carrier substrate on which the light receiving element is mounted are connected such that the output signal from the light receiving element is input to the preamplifier through electrodes on the carrier substrate, and there are provided two electrodes, on the carrier substrate, having a capacitance value of 40 fF or more therebetween in a state where no light receiving element is mounted.