To smoothly move a seat between a caring chair and a vehicle and secure a seating space during riding in a device using a detachable seat part of a wheel chair doubling as a seat of a passenger car.

Labor of inter-seat movement is eliminated by interlocking rotation of a seat-attached base and sliding to vehicle front and rear directions to secure the seating space by a link mechanism. In addition, the seat rotary base can be applied to various vehicles by adjustment of the link mechanism.