1. A fingerprint minutia input device comprising a main device body, the fingerprint minutia input device comprising: a memory storing computer program instructions; and a processor configured execute the compute program instructions to: output a fingerprint image containing fingerprint ridgelines and a pointer for designating a coordinate position of a minutia of the fingerprint image on a display screen; set, based on an external command, a minutia display mark for the minutia on the fingerprint image designated by the pointer; set, based on an external command, a gray-scale intensity of the entire fingerprint image where the pointer is located, the gray-scale intensity being adjustable within a display gray-scale range between a gray-scale upper limit value and a gray-scale lower limit value; update a width of the display gray-scale with the fingerprint image when setting the minutia display mark; and hold the display gray-scale width for outputting the minutia when no new setting information of the width of the display gray-scale is received.