Circular saw

A circular saw for use with a workpiece comprising:

• a power source;
• a saw blade, which is rotationally driven to cut the workpiece;
• a speed change mechanism which is disposed between the power source and the saw blade, the speed change mechanism changing rotation speed of the saw blade, wherein the speed change mechanism includes first and second rotating shafts disposed parallel to each other, and first and second gear trains having different gear ratios and each having a combination of a drive gear and a driven gear as one unit which are engaged with each other and transmit torque of the first rotating shaft to the second rotating shaft, wherein a torque transmission path via the first gear train is defined as a first power transmission path and a torque transmission path via the second gear train is defined as a second power transmission path;
• and
• a first clutch which allows and interrupts power transmission on the first power transmission path and a second clutch which allows and interrupts power transmission on the second power transmission path, wherein the power transmission path is switched between the first and second power transmission paths while the first and second gear trains are held engaged, by shifting of the first clutch to allow and interrupt power transmission along the first power transmission path and shifting of the second clutch to allow and interrupt power transmission along the second power transmission path.