To provide a current-voltage converting circuit capable of reducing the load of an operating amplifier, preventing a leakage current, and sufficiently discharging a capacitor 11, by a simple circuit configuration.

The current-voltage converting circuit comprises the operating amplifier and the capacitor connected between an input terminal and an output terminal of the operating amplifier. The circuit has a first pair of diodes connected in mutually opposed directions to the input terminal; a second pair of diodes connected to each of the other ends of the first pair of the diodes, in opposed directions of the first pair of the diodes; a pair of current sources connected to each of the other ends of the first pair of the diodes, in mutually opposed directions; a pair of switches connected to each of the other ends of the first pair of the diodes; and a resistor connected between each of the other ends of the second pair of the diodes and the output terminal.