To facilitate connection and disconnection of a concrete form width restricting plate to and from a form and improve an execution property and workability by punching central parts in both the end directions of a hard and rectangular flate plate in a rectangle, providing an inner click descending downward and providing an outer click descending downward from each head end of both end front surfaces of the flate plate.

A width restricting plate is made by providing outer clicks 4, 5 the head ends of which descend downward on both ends of a hard rectangular flat plate 1, punching the flat plate 1 in rectangle and providing inner clicks 2, 3 descending downward. For example, a form 10 is structurally strengthen against reception of concrete placing and constant thickness is secured by putting left and right recessed parts of the inner clicks 2, 3 and the outer clicks 4, 5 of the width restricting plate on a top plate 12 provided on a top of a form 10 at a rectilinear part and to precisely set a straight line of a passage. Connection and diconnection of the width restricting plate to and from the form 10 is simple, and it can be set by a single operation. Additionally, as it is symmetrical left and right, structural safety and stability are high and working efficiency is improved.