A circular saw includes a table for placing a workpiece thereon, a saw unit having a circular saw blade mounted thereon, and a support mechanism for supporting the saw unit on the table, so that the saw unit is movable in forward and rearward directions. A lock device includes a lock member that is movable between a first position and a second position. In the first position, the lock member permits the saw unit to move in both forward and rearward directions. In the second position, the lock member prevents the saw unit from moving in one of the forward and rearward directions.