The invention discloses a built-in plug door device for a rail vehicle. The device comprises a control mechanism, a driving mechanism, a bearing mechanism, a compaction mechanism, a guide chute and a door leaf; the bearing mechanism comprises a guide post, two sleeves, a connecting rod, a sliding block and a guide wheel; and the control mechanism is respectively connected with the driving mechanism and the compaction mechanism. The advantages of an outward swing plug door and a built-in side sliding door are combined in the built-in plug door device, and the problem of smooth appearance of the built-in side sliding door is solved by plug movement; the outer side of the body is smoother, the influence of high-speed running pressure wave on the door leaf is reduced, and high-speed running noise is reduced; the body is 140 millimeters wider than the body using the outward swing plug door; and when the plug process of the door leaf is finished, the door leaf is compacted on the body, and the possibility that the door leaf drops outwards is totally limited, so safety and sealing reliability are improved.