Four-stroke engine

A four-stroke engine (1) for a working machine with a rod (60), where a tool is attached to one end of the rod (60) in a longitudinal direction and the four-stroke engine (1) is fixed to the other end of the rod (60) in use. the four-stroke engine (1) includes: an oil circulation pathway; and a gas-liquid separating chamber (70) configured to separate oil from blowby gas. The gas-liquid separating chamber (70) includes: an inflow part (203) into which the blowby gas is introduced from the oil circulation pathway; oil discharge parts (204) configured to flow the oil separated from the blowby gas back to the oil circulation pathway; and a blowby gas discharge part (400) configured to discharge the blowby gas not containing oil mist from the gas-liquid separating chamber (70) and supplies the blowby gas to an intake passageway to a combustion chamber. The oil discharge parts (204) are formed as openings on at least two corners in a lower part of the gas-liquid separating chamber (70) in the longitudinal direction.