To prevent an overload without replacing a part even if a service condition changes in a scroll fluid machine.

This scroll fluid machine is provided with a fixed scroll 1 for erecting a spiral fixed lap 6 on one side surface, and a turning scroll 8 which is turnably arranged on a driving shaft and erects a spiral turning lap 11 for forming a compression chamber between the fixed lap 6 and the one side surface. A low pressure pressurizing stage part A formed on the outer peripheral side of the fixed lap 6 and the turning lap 11 and a high pressure pressurizing stage part B formed on the inner peripheral side of both laps are cut off. Either one of discharge ports 23 and 24 formed in the low pressure pressurizing stage part A or high pressure side suction ports 25 and 25a formed in the high pressure pressurizing stage part B is formed in a plurality, and can be selectively blocked by a blocking member 26 so that at least one is formed as a blocking port.