Centrifugal air blower

There is provided a centrifugal air blower capable of effectively suppressing noise caused by the shapes of a tongue part and a bell mouth formed in a scroll casing, and including: a fan 3 composed of a bottom plate 6 fixed to a rotating shaft, multiple blades 8, and an annular rim 9 provided concentrically with the bottom plate; a scroll casing 4 for housing the fan; a spiral flow passage 19 formed around the fan; and a tongue part 16 for suppressing an inflow of air from the end of winding to the beginning of winding of the spiral flow passage. A portion of the tongue part on the other end side in the axial direction of the rotating shaft is inclined to increase a dimension of overhanging in a counter-rotating direction of the fan toward the other end side in the axial direction of the rotating shaft.