Centrifugal blower, air-blowing apparatus, air-conditioning apparatus, and refrigeration cycle apparatus

A centrifugal air blower comprises a fan (2); and a scroll casing (4). The scroll casing includes: a sidewall (4c) covering the fan (2) from an axial direction of a rotation axis on which the fan (2) rotates, the side wall having a suction opening for sucking air; a discharge opening (41) for discharging an airflow generated by the fan (2); a tongue portion (4b) for guiding the airflow to the discharge opening (41); a peripheral wall (4a) surrounding the fan (2) from a radial direction of the rotation axis; and a bell mouth (3) formed along the suction opening (5) of the sidewall (4c). The bell mouth (3) includes an upstream end (3a) and a downstream end (3b), the upstream end being an end portion on an upstream side in a direction of flow of the air passing through the suction opening (5), the downstream end being an end portion on a downstream side in the direction of flow of the air. A distance in the radial direction of the rotation shaft between the upstream end (3a) and the downstream end (3b) at a location larger than the tongue portion (4b) in angle of a direction of rotation of the fan (2) is longer than a distance in the radial direction between the upstream end (3a) and the downstream (3b) end at a location adjacent to the tongue portion (4b).