A fingerprint sensor includes a substrate, a light blocking layer that is on a first surface of the substrate and includes openings in a light blocking mask, and a sensor layer that is on a second surface of the substrate and includes photo sensors. A fingerprint sensing method of the fingerprint sensor includes: storing a calibration image; generating an original image, based on sensing signals from the photo sensors; performing calibration on the original image by utilizing the calibration image; and detecting a fingerprint, based on the calibrated image. The calibration image is generated by synthetizing valid regions extracted from an original calibration image corresponding to the original image.