PURPOSE: To prevent the loosing trouble by folding a center frame by installing a stopper mechanism which holds a lower frame and an upper frame in an erection state or horizontally on a quarter panel, looking pin for fixing the state, and a holder, on both the frames.

CONSTITUTION: A catch 22 for the insertion of an engagement part 41 installed on a side frame 4 for holding a canvas top is installed at the upper edge part of an upper frame 2, and a pin holder 21 for inserting a lock pin 5 in the fixation of a series or parallel state for a lower frame 1 is installed on the lower edge part side. Holders 11 and 12 for the lock pin 5 are installed also on the lower frame 11 connected with the upper frame 2 through a hinge 7, and an engagement part 19 and the revolution center point O1 for the installation in free revolution for the bracket 35 on a quarter panel 6 are installed. Accordingly, the formation of the center frame is facilitated, and a canvas top can be installed, and the center frame can be accommodated in a folded state in an open car state into the quarter panel, and the loosing trouble can be prevented.