An intake device for an internal combustion engine includes a throttle body (1) that forms an intake passage (1a). A throttle valve (2) is arranged within the intake passage. A pipe member (26) is connected to the throttle body, wherein the pipe member forms a communication passage (26a) communicating with the intake passage. An engagement device (53,63; 85,87; 92,63) is provided between the throttle body and the pipe member. The engagement device includes at least one engagement protrusion (53; 85; 92) and at least one engagement recess (63; 87M). When the engagement protrusion and the engagement recess are engaged with each other, detachment of the throttle body and the pipe member from each other is restricted. The assembly process is simplified by a lack of separate components such as clamps and bolts, relying instead upon a typical snap-fit connection.