To provide an air conditioner outdoor unit including a casing having an air inlet on a side surface and an air outlet on an upper surface, a heat exchanger that covers the air inlet and is provided inside the casing, a fan that sucks in air from the air inlet and discharges air from the air outlet, and a fan motor provided on a lower side of the fan. The fan motor is set such that an outer diameter D1 thereof is larger than an outer diameter D2 of a fan boss, and an outer periphery thereof is positioned on a center side of the fan motor than a straight line c passing an upper side of a center (for example, a predetermined position a) of the heat exchanger and a side (for example, a predetermined position b) of the fan boss.