To provide an indoor unit of an air conditioner, which enables mounting of a fan having as large a diameter as possible within limited dimensions as a whole and also enables further reduction in ventilating resistance, so as to promote energy saving and sound softening.

A box-shaped body frame 100, of which the lower side is made substantially square is provided and a blower 103 and a heat exchanger 102 are provided inside a frame body constituted of a decorative panel and fitted to the lower side of the body frame, while a plurality of slender outlets 101 are provided on the lower side of the frame body along the lateral side of the lower side, so that airflow formed by the blower be let out from the outlets after the heat exchange in the heat exchanger. In the indoor unit of the air conditioner thus constituted, the outlets 101 are so formed that the end part side thereof is made wider than the central part, by widening the end part side toward the center side of the frame body.