Provided is a railway vehicle plug door device, in which even if the device is disposed in a side structure body that has a structure assembled by joining structural members by welding and that includes a bent section, that can easily ensure air-tightness between the side structure body and a door leaf. A frame body (12) is attached by way of a mechanical fastening mechanism to a section that constitutes an entrance (101) in a side structure body (100). A seal member (13) is attached to at least one of a door leaf (11) and the frame body (12), and adheres to both the door leaf (11) and frame body (12) when the door leaf (11) closes the entrance (101).