A compression regenerative machine for a fuel cell according to the present invention comprises a displacement type compression mechanism portion C connected to an oxygen-containing gas supply side of a fuel cell F, and a displacement type regenerative mechanism portion E connected to an exhaust discharge side of the fuel cell F. A confined compression chamber 14 defined by the compression mechanism portion C and a confined regenerative chamber 24 defined by the regenerative mechanism portion E have a capacity ratio of 1.25 to 3.