An intake manifold includes a first piece and a second piece. The first piece includes a first branch pipe half portion and an intake air introducing portion. The second piece is connected to the first piece by vibration-welding and includes a second branch pipe half portion, an additional body, and a connecting portion. The second branch pipe half portion is connected to the first branch pipe half portion. The additional body is connected to the intake air introducing portion. The second branch pipe half portion and the additional body are spaced apart from each other at a predetermined distance. The connecting portion connects the second branch pipe half portion to the additional body.