To provide a surface-mounting part where the sides and corners of a board are protected, and the board and a metal case are enhanced in adhesive strength between them.

A surface mounting part 10 is composed of a board 11 provided with metal case fixing electrodes 13a and 13b located its short sides and I/O terminals 14a to 14d on its long sides, a flat upside 15, side faces 16a to 16d extending downwards from the four sides of the upside 15, two fixing parts 17a and 17b provided on the side faces 16a and 16b, and a metal case 13 nearly U-shaped in cross section and made up of eight board holders 18a to 18h formed by bending the four side faces 16a and 16b partially inwards. The metal case fixing electrodes 13a and 13b provided on the board 1 and the fixing parts 17a and 17b of the metal case 12 are bonded together with solder.