An indoor unit according to the present invention includes: an air-sending portion, which includes a casing having a rectangular air outlet and accommodating an impeller including a plurality of blades; a heat exchanger, which is configured to exchange heat with gas sent from the air-sending portion; and a guide portion, which includes an upper guide defining a passage for the gas and being arranged between an upper edge portion of the air outlet and an upper end portion of the heat exchanger and a lower guide defining a passage for the gas and being arranged between a lower edge portion of the air outlet and a lower end portion of the heat exchanger, and is open at side regions of the guide portion.