A centrifugal air-sending device, comprising: an impeller having a main plate having a disk shape and a plurality of blades arranged on a peripheral edge (2a1) of the main plate; and a fan casing accommodating the impeller and having a bell mouth formed to rectify a flow of gas to be suctioned into the impeller, the bell mouth having an inlet port through which the gas flows into the fan casing, and an air-suction portion having an opening having a diameter gradually decreasing from an upstream end toward a downstream end of the air-suction portion in a direction of the flow of the gas to be suctioned into the fan casing, the air-suction portion being formed in a curved line drawing an arc in the vertical section of the bell mouth, in a vertical section of the bell mouth, in a case in which the upstream end is defined as one of a vertex of a major axis (MA, MA2) and a vertex of a minor axis (MI, MI2) of a virtual ellipse (EL, FL), the downstream end is defined as an other one of the vertex of the major axis (MA, MA2) and the vertex of the minor axis (MI, MI2) of the virtual ellipse (EL, FL), an intersection of the major axis (MA, MA2) and the minor axis (MI, MI2) is defined to be further away from a rotation shaft of the impeller than is the downstream end, and a part of an outline of the virtual ellipse (EL, FL) having a shortest distance connecting the upstream end and the downstream end along the outline of the virtual ellipse (EL, FL) is defined as a first outline, and in a range defined by a virtual first tangent (HT, HT2) of the virtual ellipse (EL, FL) touching the upstream end, a virtual second tangent (VT, VT2) of the virtual ellipse (EL, FL) touching the downstream end, and the first outline, the air-suction portion having a wall (3c1) extending between the upstream end and the downstream end, the centrifugal air-sending device being characterised in that the wall (3c1) of the air-suction portion is extending away from the intersection in a direction from the intersection across the first outline. an impeller having a main plate having a disk shape and a plurality of blades arranged on a peripheral edge (2a1) of the main plate; and a fan casing accommodating the impeller and having a bell mouth formed to rectify a flow of gas to be suctioned into the impeller, the bell mouth having an inlet port through which the gas flows into the fan casing, and an air-suction portion having an opening having a diameter gradually decreasing from an upstream end toward a downstream end of the air-suction portion in a direction of the flow of the gas to be suctioned into the fan casing, the air-suction portion being formed in a curved line drawing an arc in the vertical section of the bell mouth, in a vertical section of the bell mouth, in a case in which the upstream end is defined as one of a vertex of a major axis (MA, MA2) and a vertex of a minor axis (MI, MI2) of a virtual ellipse (EL, FL), the downstream end is defined as an other one of the vertex of the major axis (MA, MA2) and the vertex of the minor axis (MI, MI2) of the virtual ellipse (EL, FL), an intersection of the major axis (MA, MA2) and the minor axis (MI, MI2) is defined to be further away from a rotation shaft of the impeller than is the downstream end, and a part of an outline of the virtual ellipse (EL, FL) having a shortest distance connecting the upstream end and the downstream end along the outline of the virtual ellipse (EL, FL) is defined as a first outline, and in a range defined by a virtual first tangent (HT, HT2) of the virtual ellipse (EL, FL) touching the upstream end, a virtual second tangent (VT, VT2) of the virtual ellipse (EL, FL) touching the downstream end, and the first outline, the air-suction portion having a wall (3c1) extending between the upstream end and the downstream end, the centrifugal air-sending device being characterised in that the wall (3c1) of the air-suction portion is extending away from the intersection in a direction from the intersection across the first outline.