In a four-seat coupe, it is inconvenient for a rear-seat occupant to get in/out of the vehicle while a front-seat occupant is seated. In the present invention, the length of each door of the four-seat coupe is set, so that the rear-seat occupant can get off/on the vehicle while the front-seat occupant is seated. The door is provided with detachable first opening/closing mechanisms at its front and rear end portions. The first opening/closing mechanism at the front end portion of the door is adapted to be released when the front-seat occupant gets off/on the vehicle to allow the first opening/closing mechanism at the rear end portion of the door to support the door so that opening/closing motion can be performed. Also, the first opening/closing mechanism at the rear end portion of the door is adapted to be released when the rear-seat occupant gets off/on the vehicle to allow the first opening/closing mechanism at the front end portion of the door to support the door so that opening/closing motion can be performed.