An engine is equipped with a supercharger (exhaust turbocharger) which is rotationally driven by means of exhaust gas and in which an expansion ratio is settable greater than a compression ratio. The engine includes: an operation state determination unit that determines an operation state of the engine; a plurality of exhaust valves provided at a single cylinder; a variable exhaust valve timing mechanism that is capable of changing opening timing of at least one exhaust valve among the exhaust valves; and a controller that, when it is determined by the operation state determination unit that the engine is operated with low load and is acceleration time, transmits a command to the variable exhaust valve timing mechanism and advances the opening timing of the at least one exhaust valve relative to the opening timing of another exhaust valve. Thereby, supercharging response and the expansion ratio are maintained.