An intake manifold for a multiple-cylinder internal combustion engine has a collective part forming an intake gas distribution chamber, and a branch part forming branch intake passages. The collective part includes a first section defining a first space joined to a second section defining a second space. The first and second spaces define the intake gas distribution chamber. The first and second sections have corner parts, the second section being provided with a guide wall covering the inside surfaces of the corner parts. The guide wall has a guide surface and opposes the intake gas inlet, the intake gas distribution chamber being defined between the intake gas inlet and the guide wall. The guide wall and the corner parts define a back space communicating with the intake gas distribution chamber.