Disclosed is an indoor unit of an air conditioner including: a casing; a cross-flow fan arranged in the casing and having a fan rotor and a tongue portion extending in an axial direction along an outer periphery of the fan rotor below the fan rotor and forward of a center axis of the fan rotor to define a suction port, the cross-flow fan forming in the casing an air flow directed from the rear to the front; and a heat exchanger arranged upstream of the fan in a direction of the air flow and having an inclined portion inclined to be positioned further downward toward a front side. The heat exchanger is arranged such that a front end of the inclined portion is located below the fan rotor and between a foremost portion and center axis of the fan rotor in a front-to-back direction.