To prevent intense resonance even if a centrifugal compressor is operated in a wide revolution speed range.

A diffuser 2 for centrifugal compressor is disposed at an outer circumference part of a centrifugal impeller 1. The diffuser is a stationary round blade raw including a plurality of blades. The stationary round blade raw is arranged at an inner circumference side, and is composed of a first round blade raw including a plurality of first blades 2a, and a second round blade raw arranged at an outer circumference side and including a plurality of second blades 2b. The first and the second blades have height arranged at the shroud side not greater than half of diffuser channel height. Number of the first blades is greater than number of the second blades.