A flap device for an internal combustion engine includes a flow housing comprising a flow channel, an actuating shaft, a flap body arranged on the actuating shaft in the flow channel, a bore comprising a shoulder arranged in the flow housing, a bearing bush arranged in the bore, a closure bush, a slide ring comprising a slide ring inner portion, and a sealing element surrounding the actuating shaft. The actuating shaft is mounted in the bearing bush. The sealing element comprises a membrane with a membrane inner portion and a membrane outer portion. The membrane outer portion is clamped axially between the closure bush and the shoulder to form a contact surface on the bore of the flow housing. The membrane inner portion rests against the slide ring inner portion to form a mating surface which is arranged closer to the flow channel than to the contact surface.