Intake manifold

An intake manifold is formed by vibration-welding a first joining member made of a synthetic resin and a second joining member made of a synthetic resin. The first joining member includes a plurality of first intake pipe halves disposed at intervals in parallel to each other, each forming a part of one of a plurality of intake pipes. At least one of the opposite ends of each of the plurality of first intake pipe halves is connected in common. The second joining member includes a plurality of second intake pipe halves, each forming the remainder of the corresponding intake pipe and being connected to each other at a bridging part positioned in the middle in the longitudinal direction of the intake pipes. The bridging part may be provided with a low-rigidity part that has a rigidity lower than that of parts adjacent thereto. Thus. the intake manifold formed by vibration-welding a plurality of joining members made of a synthetic resin can be produced efficiently and with high precision, while suppressing the amount of synthetic resin and improving the degree of freedom in the engine layout.