Organic semiconductor layers (2, 4) are laminated sandwiching an insulator thin layer (3), and translucent electrodes (1, 5) are formed on the surfaces of the organic semiconductor layers (2, 4), respectively. While a voltage is applied so that the electrode (1) is positive with respect to the electrode (5) and the opposite surfaces of the device are irradiated with two lights (6, 7) simultaneously, photocurrent multiplication is occurred to allow a photocurrent to flow in the device. However, no photocurrent multiplication occurs to allow no flow of photocurrent when the device is irradiated with one of the lights (6, 7).