Disclosed is an image sensing device including a plurality of current cells whose total number to be used is adjusted based on a plurality of enable signals, and which are sequentially controlled based on a reset signal and a plurality of selection signals; a current-voltage conversion circuit suitable for converting a plurality of unit currents, which are supplied from current cells used among the plurality of current cells, into a ramp signal; and a first control circuit suitable for generating the plurality of enable signals based on a maximum conversion code value corresponding to a slope of the ramp signal.