A four-stroke engine for a working machine with a rod is provided, where a tool is attached to one end of the rod in a longitudinal direction and the four-stroke engine is fixed to the other end of the rod in use. The four-stroke engine includes: an oil circulation pathway; and a gas-liquid separating chamber configured to separate oil from blowby gas. The gas-liquid separating chamber includes: an inflow part into which the blowby gas is introduced from the oil circulation pathway; oil discharge parts configured to flow the oil separated from the blowby gas back to the oil circulation pathway; and a blowby gas discharge part configured to discharge the blowby gas not containing oil mist from the gas-liquid separating chamber and supplies the blowby gas to an intake passageway to a combustion chamber.