An intake manifold is manufactured by assembling resin-molded parts without using any cores, so that compactness, light-weight, low-cost and improvement of engine performance can be achieved. A inner pipe is fit-inserted into a cylindrical tubular part of an outer pipe, thereby a outer pipe support is fixed on. By fitted parts, a positioning of a direction of circumference of the outer pipe and the inner pipe is performed. The air from a inlet flows into a sarge tank through a throttle valve. Afterward, the air flows from a manifold passage inlet to a manifold passage so as to lead to intake ports of engine cylinders by passing from a straight passage through an outlet.