An image sensor includes a pixel configured to generate a pixel signal, using an analog signal processing voltage, a ramp signal generator configured to generate a ramp signal, using the analog signal processing voltage, a bias voltage generator configured to generate a bias voltage, using the analog signal processing voltage, and a noise compensator configured to generate a noise component, using a digital signal processing voltage and the analog signal processing voltage, and add the generated noise component to the generated bias voltage. The image sensor further includes a conversion circuit configured to generate a reference voltage, based on the generated ramp signal and the bias voltage to which the noise component is added, and generate an image signal by performing analog-to-digital conversion on the generated pixel signal, based on the generated reference voltage.