The invention relates to a building wall face plastering robot which comprises a fixing rack. Six parallel connection branch chains are installed on the fixing rack. The upper ends of the six parallel connection branch chains are all installed on an upper platform. A sucking pump is installed at the middle portion of the upper end face of the upper platform through screws. Three L-shaped struts are evenly welded to the right side of the upper end face of the upper platform. A sucking supporting board is welded to the tail ends of the three L-shaped struts. A first suction cup, a second suction cup and a third suction cup are installed on the inner wall of the sucking supporting board through screws. The first suction cup is connected with the second suction cup through a first connecting air pipe. A sucking pipe is connected to a sucking opening of the sucking pump and communicates with the first connecting air pipe. Four sucking jacking columns are symmetrically welded to the upper end face of the upper platform. A lifting device is welded to the upper end faces of the four sucking jacking columns. A plastering mechanical hand is installed at the upper end of the lifting device through screws. By the adoption of the building wall face plastering robot, the stable lifting and automatic plastering function can be achieved, and a new way for mechanically and automatically plastering a wall face is provided.