To provide a cutter which can easily cut a lightweight shape steel material.

A lever 5 capable of freely swinging to a handle 2 is arranged in an inside hollow case 1 having the handle 2. An cutter blade 8 to advance and retreat by repetion of operation to grip the lever 5 is arranged inside the case 1. A holder 22 to support a lightweight shape steel material is movably arranged on the front side of the case 1. After the lightweight shape steel material is inserted between the advanced holder 22 and the front of the case 1, the holder 22 is retreated, and the lightweight shape steel material is held in a position in close vicinity to the front of the case, and the cutter blade 8 is advanced by repetition of operation to grip the lever 5, and the lightweight shape steel material is cut.