An electromagnetic massage device suitable for a bathtub or pool, mountable in a bathtub or pool through a mounting hole in the wall of the bathtub or pool, comprising: a holder suitable for being fixed in the mounting hole in the wall of the bathtub or pool, where one end of the holder that, when mounted, enters into the wall of the bathtub or pool is called upper end, and the opposing end that, when mounted, comes out from the wall of the bathtub or pool is called lower end, wherein a concave cavity is formed in the opening of the upper end of the holder, the bottom of the concave cavity is a base plate, the base plate comprising a central portion which extends inside the holder to form a guide cavity, a ring cavity surrounding the guide cavity is formed between the base plate and the opening of the lower end of the holder, an edge of the concave cavity turns inside out to form, in the upper end of the holder, and the circumferential wall of the lower end of the holder is provided with a external thread; a lock nut engaging to the external thread on the circumferential wall of the lower end of the holder, configured to fasten the lower end of the holder to the outside surface of the wall of the bathtub or pool; a beating head and a rubber case having at least a concave central part provided with an internal surface spaced apart from the beating head and able to house the beating head, where the top portion of the rubber case bulges outward and the bottom portion of the rubber case is provided with a folded rim, which defines an annular peripheral part of the rubber case and is fit closely to the base plate of the concave cavity of the holder to seal the opening of the upper end of the holder; a coil provided in the ring cavity of the holder and encapsulated by a magnetic conductive cover and a magnetic conductive shell; and an armature, fastened to the beating head and mounted, together with the beating head, in the guide cavity of the holder and inside the rubber case, wherein the beating head and armature slide back and forth in the guide cavity under the action of the electromagnetic field caused by the coil so that the beating head can slide into the concave cavity from the guide cavity and enter into the rubber case, and the beating head can enter into the guide cavity from the rubber case and return to the guide cavity; and a gland nut, the circumferential wall of the concave cavity of the holder being provided with an internal thread, so that the folded rim of the rubber case can be fastened to the base plate of the concave cavity by the cooperation between the gland nut and the internal thread. a holder suitable for being fixed in the mounting hole in the wall of the bathtub or pool, where one end of the holder that, when mounted, enters into the wall of the bathtub or pool is called upper end, and the opposing end that, when mounted, comes out from the wall of the bathtub or pool is called lower end, wherein a concave cavity is formed in the opening of the upper end of the holder, the bottom of the concave cavity is a base plate, the base plate comprising a central portion which extends inside the holder to form a guide cavity, a ring cavity surrounding the guide cavity is formed between the base plate and the opening of the lower end of the holder, an edge of the concave cavity turns inside out to form, in the upper end of the holder, and the circumferential wall of the lower end of the holder is provided with a external thread; a lock nut engaging to the external thread on the circumferential wall of the lower end of the holder, configured to fasten the lower end of the holder to the outside surface of the wall of the bathtub or pool; a beating head and a rubber case having at least a concave central part provided with an internal surface spaced apart from the beating head and able to house the beating head, where the top portion of the rubber case bulges outward and the bottom portion of the rubber case is provided with a folded rim, which defines an annular peripheral part of the rubber case and is fit closely to the base plate of the concave cavity of the holder to seal the opening of the upper end of the holder; a coil provided in the ring cavity of the holder and encapsulated by a magnetic conductive cover and a magnetic conductive shell; and an armature, fastened to the beating head and mounted, together with the beating head, in the guide cavity of the holder and inside the rubber case, wherein the beating head and armature slide back and forth in the guide cavity under the action of the electromagnetic field caused by the coil so that the beating head can slide into the concave cavity from the guide cavity and enter into the rubber case, and the beating head can enter into the guide cavity from the rubber case and return to the guide cavity; and a gland nut, the circumferential wall of the concave cavity of the holder being provided with an internal thread, so that the folded rim of the rubber case can be fastened to the base plate of the concave cavity by the cooperation between the gland nut and the internal thread.