An outdoor unit of an air-conditioning apparatus includes: a terminal unit that is provided on an outer peripheral surface of a compressor, and electrically connects components provided in the compressor and outside the compressor; a side soundproof cover that covers the outer peripheral surface of the compressor except for the terminal unit; and a terminal cover that covers the terminal unit exposed from the side soundproof cover to the outside of the side soundproof cover, and soundproofs the terminal unit. The terminal cover is attached to the side soundproof cover such that the state of the terminal cover can be changed between a state in which the terminal cover covers the terminal unit and a state in which the terminal cover does not cover the terminal unit.