An indoor unit for an air-conditioning apparatus, comprising: a main body that includes an air inlet and an air outlet; a cross-flow fan that is provided inside the main body, and includes an impeller configured to, by rotation, draw air into the main body from the air inlet and blow the air from the air outlet; and a stabilizer configured to partition a space inside the main body into an inlet-side air passage which is on an upstream side of the cross-flow fan, and an outlet-side air passage which is on a downstream side of the cross-flow fan, wherein a blade included in the impeller is formed so that, when viewed in a vertical cross-sectional view of the blade, a pressure surface of the blade and a suction surface of the blade opposite to the pressure surface are curved more in a rotational direction, in which the impeller rotates, in areas farther from an axis of rotation of the impeller and closer to an exterior of the blade, and are arched so that a portion near a center of the blade is most distant from a straight line connecting an inner end and an outer end of the blade, the pressure surface and the suction surface form a curved surface including at least one circular arc, characterized in that a straight portion of the blade is formed to be connected to the curved surface on one side thereof, and extend toward the inner end of the blade on other side thereof, and is defined by a flat surface continuous with a surface formed by a circular arc out of the pressure surface and the suction surface, and when a diameter of a circle inscribed in the pressure surface and the suction surface is defined as a blade thickness (t), the blade thickness (t) is smaller at the outer end than at the inner end, is larger in areas of the blade farther from the outer end, and is approximately equal in the straight portion. a main body that includes an air inlet and an air outlet; a cross-flow fan that is provided inside the main body, and includes an impeller configured to, by rotation, draw air into the main body from the air inlet and blow the air from the air outlet; and a stabilizer configured to partition a space inside the main body into an inlet-side air passage which is on an upstream side of the cross-flow fan, and an outlet-side air passage which is on a downstream side of the cross-flow fan, wherein a blade included in the impeller is formed so that, when viewed in a vertical cross-sectional view of the blade, a pressure surface of the blade and a suction surface of the blade opposite to the pressure surface are curved more in a rotational direction, in which the impeller rotates, in areas farther from an axis of rotation of the impeller and closer to an exterior of the blade, and are arched so that a portion near a center of the blade is most distant from a straight line connecting an inner end and an outer end of the blade, the pressure surface and the suction surface form a curved surface including at least one circular arc, characterized in that a straight portion of the blade is formed to be connected to the curved surface on one side thereof, and extend toward the inner end of the blade on other side thereof, and is defined by a flat surface continuous with a surface formed by a circular arc out of the pressure surface and the suction surface, and when a diameter of a circle inscribed in the pressure surface and the suction surface is defined as a blade thickness (t), the blade thickness (t) is smaller at the outer end than at the inner end, is larger in areas of the blade farther from the outer end, and is approximately equal in the straight portion.