A centrifugal fan includes: an impeller having a back plate; and a scroll casing including a peripheral wall a first side wall facing a virtual extension of the back plate and an inner end portion of the volute shape of the scroll casing, an expanded portion, and a first edge end portion being an end of a first edge defining the discharge port, of the first side wall, are arranged in a named order in the rotation direction, the first edge end portion being farther from the rotation shaft than an other end of the first edge and distance L1≥distance LM≥distance LS>is satisfied where LS is a distance between the first side wall at the inner end portion of the volute shape and the virtual extension of the back plate, LM is a distance between the first side wall at the expanded portion and the virtual extension of the back plate, the expanded portion being a portion at which the distance between the first side wall and the virtual extension of the back plate is larger than LS, and L1 is a distance between the first side wall at the first edge end portion and the virtual extension of the back plate.