A discharge pulsation reducing cooler B is provided to cover the circumferential periphery of a compressor A. The discharge pulsation reducing cooler B has a delivery passage 41 and a jacket 43 covering that, and cooling water is circulated through a passage formed between the delivery passage 41 and the jacket 43. Delivered air flowing through the delivery passage 41 is cooled by the cooling water. In particular, because heat exchange efficiency is promoted by turbulence caused by the pulsation in the delivery passage 41, the delivered air is cooled efficiently. Also, pulsation is reduced in first and second expansion chambers 44, 45 in the delivery passage 41, and pulsation noise in the delivery passage 41 is reduced by the cooling water passage 42 and the jacket 43.