An intake manifold including a collecting pipe and a plurality of branch pipes comprises a single gas intake port, a gas outlet port opening into each branch pipe, and a gas passage extending to be divided into more than one branch passages from the gas intake port to each gas outlet port. The gas passage is configured so that the branch passages are equal in pressure loss which will be generated between the gas inlet port and each gas outlet port, and the gas passage extends to be branched in stages from the gas inlet port to each gas outlet port, forming a tournament-form configuration which is symmetrical about the gas inlet port. The collecting pipe and each branch pipe are integrally molded of resin. The gas inlet port and the gas passage are provided in a projecting section integrally molded with the branch pipes.