Abstract: A system for automatically painting the external wall of a building, in which a support is suspended from a hoist apparatus disposed on the roof of the building, and a painting apparatus is supported by the support in such a manner as to be movable horizontally. The painting apparatus includes a mechanism for advancing and retracting, in a direction normal to the wall surface, a painting hood having a spray gun disposed therein, a mechanism for swinging the hood laterally, and a frame formed of mounted on the peripheral edge of an opening of the hood which opposes the wall surface. When the painting is positioned opposite the wall surface, the frame is brought into close contact with the wall surface, thereby sealing the painting hood against the wall surface and preventing any scattering of paint mist. Since the painting hood has no rollers, it causes no degradation in the quality of the painted wall surface.