A throttle mechanism for controlling a flow rate of a cooling fluid flowing through a flow path of a turbine comprising: a first flow path forming member in which a first through hole (H61) forming the flow path and a trench (T61) communicating with the first through hole (H61) are formed; a second flow path forming member in which a second through hole (H62) forming the flow path is formed, the second flow path forming member movably installed inside the trench (T61); and a biasing member biasing the second flow path forming member in a moving direction of the second flow path forming member inside the trench (T61), wherein the biasing member includes: a first biasing member installed on one side in the moving direction inside the trench (T61); and a second biasing member installed on the other side in the moving direction inside the trench (T61), a material that forms the first biasing member and a material that forms the second biasing member are different from each other in the tendency that a Young's modulus changes according to temperature, and the throttle mechanism is configured to make the cross-sectional area of the flow path change by an overlapping portion of the first through hole (H61) and the second through hole (H62) varying in size as the second biasing member moves inside the trench (T61) according to temperature. a first flow path forming member in which a first through hole (H61) forming the flow path and a trench (T61) communicating with the first through hole (H61) are formed; a second flow path forming member in which a second through hole (H62) forming the flow path is formed, the second flow path forming member movably installed inside the trench (T61); and a biasing member biasing the second flow path forming member in a moving direction of the second flow path forming member inside the trench (T61), wherein the biasing member includes: a first biasing member installed on one side in the moving direction inside the trench (T61); and a second biasing member installed on the other side in the moving direction inside the trench (T61), a material that forms the first biasing member and a material that forms the second biasing member are different from each other in the tendency that a Young's modulus changes according to temperature, and the throttle mechanism is configured to make the cross-sectional area of the flow path change by an overlapping portion of the first through hole (H61) and the second through hole (H62) varying in size as the second biasing member moves inside the trench (T61) according to temperature. a first biasing member installed on one side in the moving direction inside the trench (T61); and a second biasing member installed on the other side in the moving direction inside the trench (T61), a material that forms the first biasing member and a material that forms the second biasing member are different from each other in the tendency that a Young's modulus changes according to temperature, and the throttle mechanism is configured to make the cross-sectional area of the flow path change by an overlapping portion of the first through hole (H61) and the second through hole (H62) varying in size as the second biasing member moves inside the trench (T61) according to temperature. <EOS>