To provide a supporting mechanism for a rotary seat of a vehicle capable of being installed in a similar space to a conventional slide support part and reducing the rotational resistance of each rotary seat.

A plurality of rollers 5 are interposed between the stationary part 3 on the floor 1 side and a rotary part 4 on the seat 2 side. The rollers 5 are arranged on a circumference centering on the rotational axis O of the seat 2 in such a way that the axes Q of the rollers 5 are perpendicular to the rotational axis O. A rolling guide means, for example a retainer 15, is installed to allow the rollers to roll on the mentioned circumference.