A frame joining structure for electrical and electronic equipment housing cabinets, in which ends of frames are simplified in shape to dispense with complex cutting and which possesses excellent strength and waterproof property. Ends of outer side surfaces (4) of three mutually orthogonal frames (1a, 1b, 1c), which constitute a framework of a cabinet, are cut at two planes of 45 relative to a plane defined by other two frames to be point-shaped. These ends are joined together directly or through a corner member (20) having the same configuration as that of the ends to constitute a firm corner portion.