To realize a circular saw cutter which makes it possible to easily remove and carry back a circular saw with safety and excellent operability in the cutter by the saw to cut a concrete form material in a predetermined size by the saw.

A bump member 3 for bumping the end of a plate material is disposed in parallel with a circular saw guide rail 2 for guiding a circular saw 1 in a linear direction, and the member 3 has the structure for moving perpendicularly to the rail 2 while holding the parallel state with the rail 2. A plate material can be placed on the lower side of the rail 2 and the bump member 3.