A structure of a combustion chamber for an engine includes a crown surface of a piston, a combustion chamber ceiling surface, an injector and an ignition plug provided on the combustion chamber ceiling surface, and an intake opening and an exhaust opening opened in the combustion chamber ceiling surface. A side where the intake opening is opened is defined as an intake port side, and a side where the exhaust opening is opened is defined as an exhaust port side. An ignition portion of the ignition plug is disposed on the intake port side. The ignition plug is ignited at a timing after the piston passes a compression top dead center. The injector is disposed on the center portion, and is configured to inject fuel toward the exhaust port side. A cavity is provided on the crown surface. A reverse squish flow generation portion is provided in the combustion chamber.