There is provided a transaction terminal device including: a housing; a frame panel that is attached to the housing; a plurality of electrodes that is provided on a board disposed within the housing; a switch member that is inserted into a penetrating hole formed in the housing, and includes a conductor which electrically connects the plurality of electrodes and an elastic deformer which maintains an electrically connected state in which the conductor is in contact with the electrodes by urging force due to elastic deformation in a state in which the frame panel is attached to the housing; and a tamper detector that detects tampering through the releasing of the electrically connected state of the plurality of electrodes due to the detachment of the frame panel from the housing. A waterproof portion that prevents water from infiltrating into the penetrating hole is provided at the switch member.