To provide stable rotation of a compressor wheel in a compressor of an exhaust turbo supercharger.

An exhaust turbo supercharger 3 is provided in an engine 1. A turbine 4 of the exhaust turbo supercharger 3 is driven by means of exhaust gas H or the engine 1 in order for a compressor 6 of the exhaust turbo supercharger 3 to compress air and to feed compressed air A to an air feeding port 10 through an air feeding pipe 9. A surface tank 13 is interposed in the middle of the air feeding pipe 9. A reflected wave reflected on a closed intake valve 22 and returned to the surge tank 13 is expanded and diffused to be pressure- reduced in the surge tank 13, and thus the transmission of the reflected wave to the compressor 6 of the exhaust turbo supercharger 3 is reduced.