PURPOSE: To make a seat cushion frame not to interfere with the rear member of an upper frame even if a vehicle seat is pushed in up to the rearmost end, and make the upper frame not to interfere with a center pillar lower garnish when the vehicle seat is rotationally moved.

CONSTITUTION: This invention concerns the supporting device of a vehicle seat used so that at getting in and out of a vehicle for a utilizer of a wheelchair and the like, a vehicle door is opened, and the vehicle seat 1 is rotationally moved by 90 degrees and slidably drawn out from the vehicle door opening part. In the supporting device of the vehicle seat constituted of a lower frame 5, an upper frame 8, a fastening tool 7, a release lever, and a pair of slide rail assemblies, an extending member 2 is arranged on the rear frame 8, of the upper and a member to be cut out is arranged on the side member 20 on the vehicle door side of the frame 8.