An engine includes a cylinder head, an ignition plug disposed in the cylinder head, a head partition wall disposed on the cylinder head to surround a periphery of the ignition plug, an injector disposed in the cylinder head and having an injection hole exposed outside the head partition wall, a cylinder block coupled to the cylinder head, a cylinder formed in the cylinder block, a piston disposed in the cylinder, and a piston partition wall disposed on a crown surface of the piston to face the head partition wall in a sliding direction of the piston. The height of the piston partition wall from the crown surface on the side closer to the injector is less than the height of the piston partition wall from the crown surface on the side farther from the injector.