Blower includes: scroll casing, centrifugal impeller and a motor. Scroll casing includes: recessed portion formed outside lateral plate concentrically with centrifugal impeller; inner-circumferential flat portion disposed more on an inner circumference than recessed portion; and outer-circumferential flat portion disposed more on an outer circumference than recessed portion. Bottommost surface of recessed portion is disposed on a same plane as lateral plate end surface of lateral plate. Angle θa made by inner-circumferential flat portion and recessed portion inner surface of recessed portion on an inner circumference is set to a value which falls within a range of 90° or more to 120° or less.