To obtain a fixation structure in which a power-supply plug can be temporarily fixed firmly when the power-supply plug is inserted into an insertion hole, in which the power-supply plug is hard to remove, and whose costs can be lowered due to simple structure.

Shapes of a pair of insertion holes 3, 3 into which a power- supply plug is inserted so as to be fixed temporarily are formed in such a way that at least inside hole edges 31, 31 are elevated and curved respectively toward the side of the holes. Inside hole parts 4 which outer edges 42, 42 are curved toward the side of the insertion holes 3, 3 are formed at the inside of the pair of insertion holes 3, 3. When a pair of insertion pieces of the power- supply plug are inserted into the insertion holes 3, 3, inner side faces of the pair of insertion pieces are brought elastically into pressure contact with the curved hole edges 31, 31.