An indoor unit for an air-conditioning apparatus includes: a casing, which is to be attached to a wall in a room at a back surface side of the casing; an air inlet and an air outlet, which are formed in the casing; an indoor heat exchanger and an indoor fan, which are arranged in an air passage continuous from the air inlet to the air outlet; an up-and-down airflow direction plate, which is provided in the air outlet so as to be turnable, forms an air outlet passage for blowing air to be blown out through the air outlet in a region located below the air outlet, and is configured to change a direction of the blowing air; and an up-and-down airflow direction assist plate, forms the air outlet passage and is configured to change the direction of the blowing air between the up and down directions.