1. A fingerprint image acquiring device comprising: a fingerprint image input unit to which fingerprint images are input consecutively; an image correlating unit to correlate a plurality of fingerprint images input from the fingerprint image input unit, the image correlating unit matching the input fingerprint images in position; a resolution enhancing determining unit to determine whether an area making resolution enhancing possible is present by detecting an area overlapping between fingerprint images as a result of image correlating and estimating similarity between the fingerprint images; an image synthesizing unit to synthesize the fingerprint images based on a result of the position matching by the image correlating unit; and a resolution enhancing unit to enhance a resolution of the area making resolution enhancing possible in the fingerprint image, wherein a fingerprint image is generated by partially enhancing the fingerprint image input to the fingerprint image input unit in resolution.