An electromagnet is secured to one end of a tug rope which is to be paid out from a tugboat towards a ship to be tugged, and the electromagnet consists of a plurality of relatively movable magnetic pole members, and hence the whole magnetic pole surface of the electromagnet is composed of a plurality of magnetic pole surfaces of said magnetic pole members. Thus, the end surfaces of said magnetic pole members may accommodate themselves to the curved surface or non-irregular surface of the hull of a ship to be tugged due to the relative, independent movements of the respective magnetic pole members, thereby bringing each of the end surfaces of the magnetic pole members into intimate contact therewith, whereby the end of the tug rope may be rigidly secured to the hull of the ship by means of the electromagnet thus facilitating connection of the tugboat with the ship to be tugged, in positive, safe and simple manner.