In a leak test method, a crank angle is set to a specific phase. When a crankshaft is positioned in the specific phase, an intake or exhaust valve of each cylinder including a combustion chamber having an inner volume that has become larger than an average value of inner volumes of combustion chambers of all the cylinders is open. When the crankshaft is at the set crank angle, a fluid for leak test is injected through intake and exhaust ports where the intake and the exhaust valves are disposed and that communicate with the combustion chambers, and through an engine opening other than the intake and the exhaust ports, with an opening of the engine other than the intake and exhaust ports and the engine opening to which the fluid is supplied in the leak test sealed. After fluid injection is completed, a pressure in the engine is measured.