PURPOSE: To fit a body to be fitted surely and easily even to a fitting member having no flange, by providing a pair of rocking members, a connection member and the pressing member which presses at least one part of the rocking members, and properly setting the relative position of the action line by the pressing member and the tip of the rocking member.

CONSTITUTION: A pair of rocking members 12 abuts on the side face V3 of a fitting member V at their tips by interposing a fitting member (vice) V, also, at least one part is pressed toward the side face V3 by a pressing member 13 and so the body to fitted is fixed to the fitting face V4 of the fitting member V by its interposing from the side face V3 side. At this time, the whole rocking members 12 receive a rotation force in the direction apart from the fitting face V4 with the tips as the center because the rocking members 12 abutting on the side face V3 between the action line by the pressing member 13 and the fitting face V4 at their tips and the body to be fitted can strongly be fixed with its being closely fitted to the fitting face V4 via a connection member 11 by this rotation force.