A retaining member includes at least a leg portion having a latch portion, a coupling portion and a spring portion. When the spring portion is displaced, the coupling portion is twisted. Then, the latch portion and the coupling portion are inserted into the opening so that an electric component is retained on a main face of the substrate. In this state, a part of the latch portion is disposed at the periphery of the opening on a rear face of the substrate, a part of the coupling portion is disposed in the opening, and the spring portion is disposed on the main face of the substrate. Therefore, the retaining strength of the electric component to the substrate can be improved, and damage of a side wall of the opening can be decreased.