Provided is an outdoor unit of an air conditioner which has good assembly stability by more cheaply and easily increasing mechanical strength of a housing, and in which the cost thereof is further suppressed by reducing the number of components such as screws, as an outdoor unit of a large air conditioner including two blowers. The left front pillar and the right front pillar are fixed between the front beam and the base panel hung between the front ends of the left side panel and the right side panel, and the rear pillar is fixed between the rear beam and the base panel hung between the rear ends of the left side panel and the right side panel. Therefore, the front beam and the rear beam are prevented from being distorted or bent, and thus mechanical strength of the entire housing is enhanced.