PURPOSE: To enhance the performance of a centrifugal compressor by straightening a pressurized fluid inside a delivery pipe that is delivered from the centrifugal turbo machinery, thus preventing swirl.

CONSTITUTION: An inward straightening vane 21 for regulating the swirl of compressed air is provided on the inner peripheral surface of a delivery pipe 2 connected to the swirl-chamber outlet of centrifugal turbo machinery, to constitute a device for preventing swirl in the delivery pipe of the centrifugal compressor. The straightening vane 21 may be provided to partition the inside of the delivery pipe 2 radially.