A photodetector control circuit in a photodetector for detecting light from a photodiode using a phototransistor and controls drive of the photodiode and detection of a current of the phototransistor has a received light amount detecting unit that detects a detection current, which flows through the phototransistor in accordance with a received light amount, by converting the detection current into a detection voltage, and compares the detection voltage with a reference voltage detected during reception of a reference light amount, to thereby detect a change in the received light amount, a diode current control unit for controlling a diode current that is caused to flow through the photodiode, and a control unit that detects a temperature based on a forward drop voltage of the photodiode and estimates a current change rate of the phototransistor based on the detected temperature.