To enable a convertible vehicle provided with a driver seat and a passenger seat having seat cushions and seat backs to secure security in a cabin even when an occupant leaves the convertible vehicle while leaving an upper part of the cabin open by storing a mobile roof in a storing part.

A first back plate 19 fixed with a back face of the seat back 11 and a second back plate 20 arranged behind the first back plate 19 are arranged to rotatably connect lower parts of the first and the second back plates 19, 20 and to rotatably connect the second back plate 20 with a vehicle body 1. When the occupant leaves the convertible vehicle, the first and the second back plates 19, 20 are brought to positions above the seat cushions 10 to cover the upper part of the cabin.