A copper base alloy suitable for use as a material for a sliding member used under severe sliding conditions such as a floating bush bearing of a turbocharger used in automobiles is disclosed. The alloy comprises, by mass %, 15 to 25% Zn, 4.2 to 10% Di, 2 to 7% Mn, 1 to 3% Si and balance of Cu and unavoidable impurities, the alloy having a structure of which matrix is composed of -single phase, wherein a eutectic structure of the -phase and an Mn—Si compound and Bi particle are distributed throughout the matrix.