To prevent vibrations and noise of a piping accompanied with the generation of cavitation, and prevent erosion and abration by a jet.

This straightening vane 1 for a rotary valve is arranged at an upstream side of the rotary valve 3 of a fluid transport pipeline 2, and applies a pressure loss to a fluid L. This straightening vane 1 comprises: outer frames 1a; cutoff parts 1b each of which is formed integrally with each of the outer frames 1a and applies the pressure loss to the fluid L; and a passage part 1c through which the fluid L passes.