The present invention is to provide a loudspeaker, which includes a frame having a through hole centrally provided at a bottom side thereof, a coil tube with a coil unit fixedly mounted around the outer periphery thereof and having a first end fixed to the through hole and a second end received in a receiving space of the frame, a diaphragm attached to periphery of an opening of the frame, and a plurality of oppositely oriented magnetic elements fixed on the diaphragm, wherein every two adjacent magnetic elements are spaced apart by an appropriate distance, and the magnetic elements are located in the coil tube at positions that magnetic lines generated by the coil unit are highly concentrated. Since vibration of the magnetic elements caused by the magnetic forces generated from the coil unit is enhanced, output power of the loudspeaker will increase accordingly.