A walk-behind machine includes a clutch having a driving state where a motor drives wheels to rotate and an unlocked state where the wheels freely rotate relative to the motor. The clutch includes a movable member and a driving member. The movable member is capable of moving between a locked position where the clutch is in the driving state and an unlocked position where the clutch is in the unlocked state. The driving member transfers power to the wheels by means of friction. When the clutch is in the driving state, the motor drives the wheels to rotate in a first direction, when the motor stops rotating, the wheels rotate in a second direction opposite to the first direction and can drive the driving member to move by frictional force so that the driving member pushes the movable member to move from the locked position to the unlocked position.
