To provide a welded molded product made of a synthetic resin capable of simply performing the treatment of the synthetic resin apt to be caused at the initial stage of vibration welding and capable of preventing scratched refuse from getting mixed in a housed article even if the synthetic resin is used as it is.

In the rectangular welded molded product 10 obtained by mutually joining a pair of halved bodies 10A/10B comprising the synthetic resin and having an almost half box shape by vibration welding, first welded ridges 11 are formed to the opening end surfaces of the halved bodies 10A/10B at the parts almost crossing the vibration direction of vibration welding at a right angle while second welded ridges not thicker than the first welded ridges 11 are formed to the parts of the opening end surfaces becoming almost parallel to the vibration direction. These first and second welded ridges 11 are respectively made almost continuous and strip wall parts for wrapping scratched refuse, which is generated when these ridges 11 are vibrated relatively, are integrally formed to at least the insides of the first and second welded ridges 11 formed to either one of both halved bodies 10A/10B.