An intake manifold 1 is provided with a surge tank 2 and a plurality of branch pipes 3 branching from the surge tank 2, and is made up of a plurality of separate pieces 1A-1C. Each of the branch pipes 3 is provided with an intake outlet 6 for outflow of intake air to each cylinder of an engine. The intake manifold 1 further includes a single gas inflow port 11, a plurality of gas outflow ports 13 opening one in each of the branch pipes 3, and a gas passage 14 extending in a branch form from the gas inflow port 11 to each of the gas outflow ports 13. Each of the gas outflow ports 13 is located away from the intake outlet 6 of the corresponding branch pipe 3 by a predetermined passage length L1.