A circuit board to be attached to a support such as a case body is provided. The circuit board has formed therein a mounting hole which is so designed as to permit a thermally deformable stud to protrude through the mounting hole and also to be thermoplastically staked to mount the board to the support. A layer is printed on the board by means of silk screen printing at a distance from the mounting hole. In a case where a moisture-proof and insulating material is applied over a surface of the board, the printed layer servers to block a flow of the moisture-proof and insulating material into the mounting hole. This avoids a reduction in strength of fastening the board to the support. The printed layer may also be used in visually inspecting a failure in thermoplastic staking to mount the board to the support.