An axial cross-sectional shape of a scroll flow path 13 is a roughly circular shape, a diffuser outlet connected to the roughly circular shape is shifted to a position which is closer to a circle center than to a position of a tangent line to the circular shape and which does not reach the circle center, the circular shape is formed from a scroll chamber 30 which juts out in the axial direction relative to the position of the diffuser outlet 11a and a shift chamber 32 that forms a remainder of the roughly circular shape in a direction opposite to the scroll chamber 30, and the shift chamber 32 is at least formed on the scroll flow path 13 of a winding end portion 19 in a circumferential direction of a spiral.