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