A unit pixel apparatus may include a plurality of unit pixels including a reset transistor, each unit pixel being suitable for outputting a pixel signal corresponding to incident light; a reset transistor gate voltage transmission unit suitable for transmitting a plurality of reset transistor gate voltages; and a first voltage switching unit suitable for transmitting a first supply voltage among the plurality of reset transistor gate voltages to a gate terminal of the reset transistor in each of the unit pixels during a period from an exposure start time to just before a readout time.