An image sensor for sampling a pixel signal a plurality of times during a readout time includes an analog comparator configured to compare a signal level of the pixel signal with a signal level of a target ramp signal that is any one of a plurality of ramp signals, a counter configured to output counting data based on a comparison result of the analog comparator, and a digital comparing circuit configured to compare a binary value of a target reference code corresponding to the target ramp signal with a binary value of the counting data and determine whether to output a digital signal corresponding to the counting data to a data output circuit based on a result of the comparison between the binary value of the counting data and the binary value of the target reference code.