An intake control device for an internal combustion engine having a first intake passage (5); a second intake passage (8); an intake passage length-changing valve (11); a partition (14) that partitions the intake passage into two partitioned intake passages (12, 13); and a tumble control valve (17). When one of the partitioned intake passages (12) is closed by the tumble control valve (17), air drawn into a combustion chamber through the open partitioned intake passage (13) forms a tumble flow. The length of the second intake passage (8) is longer than the length of the first intake passage (5) from a surge tank (1) to the connection point (S) between the second intake passage (8) and the first intake passage (5), and the passage cross-sectional area of the second intake passage (8) is smaller than the passage cross-sectional area of the first intake passage (5) from the surge tank to the connection point (S).