To provide a flow control method and a flow control valve capable of controlling fluid of a large flow even under high temperatures, and reducing pressure loss generated in the fluid.

A valve element 2 is held by a hollow bellows part 3, and by regulating quantity of gas G contained in the bellows part 3, the bellows part 3 is expanded/contracted. The valve element 2 is thus brought to be closer to/apart from an opening 1 where the fluid F from the upstream side is introduced, thereby flow of the fluid F introduced from the opening 1 is controlled.