An outdoor unit of an air conditioner is provided that improves work efficiency at the time of installation and maintenance of the outdoor unit and prevents a cover for covering an opening from being unintentionally left open. The outdoor unit of the air conditioner includes an electrical box, a housing that covers the electrical box to form an contour, an electrical box cover member that covers components inside the electrical box, a housing cover that covers the electrical box cover member from outside, wherein the electrical box cover member has a work opening and has an opening cover that covers the work opening mounted thereon, and in which the housing cover abuts on the opening cover in a state of the opening cover being open.