Abstract: The Problems To dissipate or remove droplets of sweat fluid discharged from sweat glands of the finger placed on the sensor surface, which is the cause of the residual fingerprint image, from the surface of the fingerprint image sensor. Means for Solving the Problem On the surface of a fingerprint image acquisition sensor consisting of the electrode 2 of the minimum functional element separated with the grid 1, a coating layer on which the groove 30 is etched on the surface of the coating layer 32, running along the center of each grid line for draining the sweat fluid discharged from the sweat glands on the finger placed on the fingerprint image acquisition sensor.