A biometric authentication apparatus, comprising: a biometric sensor configured to capture an image of a hand of a user; a touch panel configured to output a contact signal indicating contact positions of fingers of the user in response to the reception of an operation by the fingers of the user; and a control unit (11, 34, 35, 36, 37) configured to: display, on the touch panel, a plurality of marks (31-1, 31-2) each of which indicates a position at which any of the fingers of the user is intended to come into contact with the touch panel; acquire the contact signal output from the touch panel; reduce in size one or more marks among the plurality of marks (31-1, 31-2) during acquiring biometric information from the image captured by the biometric sensor when the control circuit detects, in accordance with the contact signal, that the fingers of the user are in contact with the plurality of marks; and display, on the touch panel, the one or more marks whose size has been reduced together with the remaining ones of the plurality of marks, and a respective guide (311; 312) indicative of either or both of a trajectory and a direction of a user operation of sliding a finger from each of the one or more marks whose size has been reduced and from each of the remaining ones of the plurality of marks. a biometric sensor configured to capture an image of a hand of a user; a touch panel configured to output a contact signal indicating contact positions of fingers of the user in response to the reception of an operation by the fingers of the user; and a control unit (11, 34, 35, 36, 37) configured to: display, on the touch panel, a plurality of marks (31-1, 31-2) each of which indicates a position at which any of the fingers of the user is intended to come into contact with the touch panel; acquire the contact signal output from the touch panel; reduce in size one or more marks among the plurality of marks (31-1, 31-2) during acquiring biometric information from the image captured by the biometric sensor when the control circuit detects, in accordance with the contact signal, that the fingers of the user are in contact with the plurality of marks; and display, on the touch panel, the one or more marks whose size has been reduced together with the remaining ones of the plurality of marks, and a respective guide (311; 312) indicative of either or both of a trajectory and a direction of a user operation of sliding a finger from each of the one or more marks whose size has been reduced and from each of the remaining ones of the plurality of marks. display, on the touch panel, a plurality of marks (31-1, 31-2) each of which indicates a position at which any of the fingers of the user is intended to come into contact with the touch panel; acquire the contact signal output from the touch panel; reduce in size one or more marks among the plurality of marks (31-1, 31-2) during acquiring biometric information from the image captured by the biometric sensor when the control circuit detects, in accordance with the contact signal, that the fingers of the user are in contact with the plurality of marks; and display, on the touch panel, the one or more marks whose size has been reduced together with the remaining ones of the plurality of marks, and a respective guide (311; 312) indicative of either or both of a trajectory and a direction of a user operation of sliding a finger from each of the one or more marks whose size has been reduced and from each of the remaining ones of the plurality of marks.