To provide a power tool materializing rational driving in the power tool having an engine and a motor.

A chain saw is configured as a power tool having an engine 111 and an electric motor 141. The cain saw has a final output shaft 131 for driving a saw chain, a battery pack 137 for supplying a current to the electric motor 141, and a controller 139 connected to the battery pack 137. The chain saw is configured so as to drive the saw chain by making the engine 111 and the electric motor 141 simultaneously drives the final output shaft 131. The controller 139 is configured so as to control the driving of the electric motor 141 on the basis of the battery residual quantity of the battery pack 137.