Provided is an infrared light detector 100 with a plurality of first electronic regions 10 which are electrically independent from each other and arranged in a specific direction, formed by dividing a single first electronic region. An outer electron system which is electrically connected to each of the plurality of first electronic regions 10 in a connected status is configured such that an electron energy level of excited sub-bands of each of the plurality of first electron regions 10 in a disconnected status is sufficiently higher than a Fermi level of each of second electronic regions 20 opposed to each of the first electronic regions 10 in a conduction channel 120.