PURPOSE: To eliminate generation of a part in which coating is insufficient by incorporating a board in a case and then pouring resin material in the case.

CONSTITUTION: A printed board 2 mounted with an electronic component is mounted in a case 3. In this case, an electric connection of the board 2 to the case 2 is conducted by screw clamping as a noise remedy, and a mounting operation for bringing a component to be required for heat dissipating into close contact with an inner surface 3a of the case 3 is executed. Then, a resin material 4 having low hardness and high thixotropy is poured in the case 3. Thus, a part above an upper part of the component 1 and a surface of the board 2 are covered with a predetermined layer thickness. That is, the component 1 of the components 1 on the board 2 which is merely mounted on the board 2 is covered entirely with a resin layer 4a, and the component to be mounted in a close contact state with the surface 3a of the case 3 for heat dissipating is covered on the surface of the component except the contact surface with the case 3.