To reduce the possibility damaging a part of a molded product at a position where a bush is embedded even if the load caused by the wt. or vibration of the molded object acts by forming unevenness to the outer peripheral surface of the bush.

At first, bushes 24a, 24b are arranged within a mold at definite positions to perform mold clamping and a reactive raw soln. is injected into the cavity of the mold to perform reactive injection molding. Thereafter, the mold is opened to take out the molded object 20 integrated with the bushes 24a, 24b from the mold. Since unevenness is formed on the outer peripheral surfaces of the bushes 24a, 24b by recessed parts 30a or protruding parts 3b, the bonding strength of the outer peripheral surfaces of the bushes 24a, 24b and the molded object 20 is enhanced. Therefore, the external force such as the wt. or vibration of the molded object acting on the bushes is dispersed not only to the surface but also to interior of the molded object 20 to transmit. As a result, even if the load due to the wt. or vibration of the molded object acts, possibility such that the molded object 20 is damaged at the positions where the bushes are embedded is reduced.