PURPOSE: To provide a seat wherein a buckle part of a safety belt placed on a seat cushion is prevented from dropping down to a floor even when the seat cushion is moved to an inverted position in a condition that the safety belt is not engaged with a fixing hook.

CONSTITUTION: A seat has seat cushions 3 movable to an inverted position by front side hinges 2, seat backs 5 movable to almost a horizontal position by lower hinges 4, safety belt formed by fixing an anchor part to a floor 6 to further arrange a buckle part on the seat cushion 3 and a box 20 supported with the floor 6 to be further arranged so that the buckle part of the safety belt can be in-out stored.