An indoor unit for an air-conditioning apparatus, comprising: a casing having an air inlet located on a top face portion, an air outlet extending from a bottom face portion to a lower front face portion, and an airflow path that communicates the air inlet and the air outlet with each other; an axial fan disposed within the airflow path under the air inlet; an indoor heat exchanger disposed within the airflow path under the axial fan, the indoor heat exchanger having a W-shape in side view; a forward drain pan disposed within the airflow path below a forward valley portion of the indoor heat exchanger; and a rearward drain pan disposed within the airflow path below a rearward valley portion of the indoor heat exchanger, wherein the airflow path is divided by the forward drain pan and the rearward drain pan into a first airflow path, a second airflow path, and a third airflow path, the first airflow path being defined between a front wall of the airflow path and the forward drain pan, the second airflow path being defined between the forward drain pan and the rearward drain pan, the third airflow path being defined between the rearward drain pan and a back wall of the airflow path, characterized in that the indoor unit comprises an up/down airflow direction flap that adjusts an up/down angle of air blown out from the air outlet, the up/down airflow direction flap including a forward up/down airflow direction flap and a rearward up/down airflow direction flap that are disposed separately in a portion of the air outlet located on the bottom face portion of the casing and at least a front end portion of each of the forward up/down airflow direction flap and the rearward up/down airflow direction flap is swingable in an up/down direction, wherein the rearward up/down airflow direction flap is disposed under the second airflow path and the third airflow path such that in side view, the front end portion of the rearward up/down airflow direction flap is located at a same position as a front end portion of the second airflow path or located forward of the second airflow path, and wherein the forward up/down airflow direction flap is disposed such that in side view, the forward up/down airflow direction flap is located forward of the rearward up/down airflow direction flap and under the first airflow path. a casing having an air inlet located on a top face portion, an air outlet extending from a bottom face portion to a lower front face portion, and an airflow path that communicates the air inlet and the air outlet with each other; an air inlet located on a top face portion, an air outlet extending from a bottom face portion to a lower front face portion, and an airflow path that communicates the air inlet and the air outlet with each other; an axial fan disposed within the airflow path under the air inlet; an indoor heat exchanger disposed within the airflow path under the axial fan, the indoor heat exchanger having a W-shape in side view; a forward drain pan disposed within the airflow path below a forward valley portion of the indoor heat exchanger; and a rearward drain pan disposed within the airflow path below a rearward valley portion of the indoor heat exchanger, wherein the airflow path is divided by the forward drain pan and the rearward drain pan into a first airflow path, a second airflow path, and a third airflow path, the first airflow path being defined between a front wall of the airflow path and the forward drain pan, the second airflow path being defined between the forward drain pan and the rearward drain pan, the third airflow path being defined between the rearward drain pan and a back wall of the airflow path, characterized in that the indoor unit comprises an up/down airflow direction flap that adjusts an up/down angle of air blown out from the air outlet, the up/down airflow direction flap including a forward up/down airflow direction flap and a rearward up/down airflow direction flap that are disposed separately in a portion of the air outlet located on the bottom face portion of the casing and at least a front end portion of each of the forward up/down airflow direction flap and the rearward up/down airflow direction flap is swingable in an up/down direction, wherein the rearward up/down airflow direction flap is disposed under the second airflow path and the third airflow path such that in side view, the front end portion of the rearward up/down airflow direction flap is located at a same position as a front end portion of the second airflow path or located forward of the second airflow path, and wherein the forward up/down airflow direction flap is disposed such that in side view, the forward up/down airflow direction flap is located forward of the rearward up/down airflow direction flap and under the first airflow path.