An automatic cover-opening device has a body, at least one cover panel and a recoil mechanism. The body has an insertion hole defined in the body. The at least one cover panel is mounted on the body and moveably closes the insertion hole. Each one of the at least one cover panel has a guiding segment having at least one guiding edge inclined relative to an axis of the insertion hole to guide an axial force along the axis of the insertion hole to a lateral direction non-parallel with the axis, so as to generate a lateral component force for opening the at least one cover panel. The recoil mechanism is disposed on the body to push the at least one cover panel to a closed position for closing the insertion hole. With such an arrangement, an automatic cover-opening device that can be applied for insertion of a rod-like object is provided.