A compass cutter has a main body fastened with an extension rod which is connected with a slidable seat slidable along the extension rod. The main body is further provided with a locating block, a protective cover, a blade, a fixation block, and an insertion pin. The slidable seat is provided with a locating block, a connection rod, a locating pin, and a shield. The compass cutter can be expanded, through the movement of the extension rod. The locating pin and the blade are covered by the shield to protect the user of the compass cutter.