CENTRIFUGAL COMPRESSOR AND SUPERCHARGER

An annular diffuser (27) is formed on an outlet side of a wheel (13) in a housing (5). A spiral scroll (31) is formed on an outlet side of the diffuser (27) in the housing (5). An annular concave part (37) is formed to be depressed to an inside in a radial direction in a boundary (35) between a shroud-side wall surface (27s) of the diffuser (27) and a wall surface (31w) of the scroll (31).