The invention belongs to the technical field of an underground coal mine short-wall exploitation device, and particularly relates to a single-arm onboard roof bolter for an underground coal mine, which solves the problems of the existing anchor support device. The single-arm onboard roof bolter comprises a rotating base, a cantilever, an operating platform assembly, a drilling arm rotating device and a drill frame, wherein the movable rotating base capable of rotating horizontally is a base for connecting the single-arm onboard roof bolter and equipment, the cantilever is supported on the rotating base, the cantilever is of an inner-outer sleeve structure, one end of the cantilever is connected with the rotating base through a horizontal hinge shaft, the other end of the cantilever is hinged to the operating platform assembly, the drill arm rotating device is installed on the front end of the operating platform assembly, and the drill frame can be installed on the front end of the operating platform assembly in a rotating manner. The single-arm onboard roof bolter is used for supporting other coal mine equipment mining machinery, roadway repairing machinery and the like, can move back and forth on a track provided by the equipment by adopting the hydraulic oil as a power source, has multiple degrees of freedom such as extension, rotation and the like and can realize the anchor installation construction of a whole section.