Even if streak-like noise or streaks caused by dragging which can be hardly distinguished from upheaval lines exist, background regions and impressing regions are separated from each other without being affected by existence of streaks. A fingerprint image background detection apparatus which discriminates background regions and impressing regions in an input fingerprint image includes impressing feature extraction means 22 which finds a pixel value variation quantity in a direction parallel to streak-like noise or streaks caused by dragging every small region obtained by dividing the input fingerprint image, tentative impressing region decision means 23 which judges impressing regions by comparing a pixel value variation quantity of every small region found by the impressing feature extraction means with a threshold, and impressing region shaping means 24 which shapes the impressing regions judged by the tentative impressing region decision means to obtain a convex shaped figure and obtains regions other than the impressing regions as background regions.