Photosensor circuit includes: a photoelectric conversion element; a first MOS transistor for converting a current signal into a voltage signal, a first capacitor element; a second capacitor element; a second MOS transistor for controlling charge transfer from the first capacitor element to the second capacitor element; and a control section for supplying gate voltages and drain voltages to the first and second MOS transistors. The control section performs initial setting and voltage control such that the charge transfer can be carried out efficiently for setting of the gate voltages and drain voltages to be supplied the first and second MOS transistors. Time length of the charge transfer is set so as not to exceed 100 μsec.