To obtain an excellent acoustic characteristic by preventing a waterproof membrane from being elongated more than required or damaged due to an external pressure even when the area of the waterproof membrane is increased.

The waterproof structure consists of a device case 1 where an acoustic through-hole 2 is formed at prescribed part, a waterproof membrane 3 that clogs the through-hole 2 in the device case 1, and a protection member 5 that have porosity to restrict deformation of the waterproof membrane 3 and provided in an inner side of the device case 1 from the waterproof membrane 3. Thus, in the case that an external pressure such as water pressure and atmospheric pressure is higher than an inner pressure in the device case 1 when the external pressure is applied to the waterproof membrane 3, even if the waterproof membrane 3 is going to be deformed so as to be pushed toward the inside of the device case 1, since the protection member 5 provided in the inside limits deformation of the waterproof membrane 3, even when the area of the waterproof membrane 3 is increased, the waterproof membrane 3 is surely prevented from being elongated more than required or damaged thereby obtaining an excellent acoustic characteristic.