Disclosed is a portable outdoor glass cleaning device. By combined work of parts like guide rails, lead screws, motors and a controller, a cleaning brush is enabled to automatically clean the surface of glass outside a window, so that the problems of large danger coefficient and high labor intensity when cleaning personnel cleans outer-surface glass of the window are solved. The portable outdoor glass cleaning device comprises a fixed support, a moving support, a moving cleaning slider, a storage battery, the controller and limiting switches. The portable outdoor glass cleaning device is directly fixed on a wall below a windowsill by a fixing clamp, and automatic cleaning of outdoor glass is realized by utilizing rotation of the lead screws and the cleaning brush and automatic programming control. The portable outdoor glass cleaning device has the advantages of convenience in mounting, economy, practicability, convenience and quickness in use, safety and reliability in running, good cleaning effect and the like.