A small and high-performance waterproof speaker which can be manufactured inexpensively by decreasing the number of components. Front face of a case (1) is sealed hermetically by a water resistant diaphragm (2) from which a voice coil (3) is projecting inward and a magnetic circuit part (5) having a part (6a) being fitted to the voice coil (3) and a permanent magnet (8) is secured to a first resilient plate (4) provided in the case (1). The first resilient plate (4) is provided with a plurality of through holes (18) and the fitting part (6a) is coupled with the diaphragm (2) through a first coupling member (13) of resilient material. On the other hand, an inertial member (12) is secured to a second resilient plate (11) disposed, oppositely to the first resilient plate (4), in the case (1) and the second resilient plate (11) is coupled with the first resilient plate (4) through a second coupling member (14) of resilient material.