The indoor unit of an air-conditioning unit includes: an opening; a cover; a heat medium heat exchanger; and an air processing unit. The air purge valve is positioned on a rear side in a projection direction of the opening inside the casing. The cover includes, on its one side, a single hook protruding from its cover body. The cover includes, on its side opposite to the one side, a temporarily fixing tab configured to temporarily fix the cover to the casing with the cover body closing the opening.