To hear an underwater sound and an external sound, and to prevent the occurrence of a pain of a middle ear and an internal ear by long hour use by arranging an external ear crease close contact part and an auricle close contact part, and forming a waterproof earplug of a soft resin so as to form a cavity in the center.

A tetrafluoroethylene resin porous film is formed in a circular shape to be adhered to or thermally installed in parts 1, 2 of an earplug. Then, selective permeability for permeating air and repelling water is imparted. A lumen is arranged, and a hydrophobic synthetic resin lump 3 is fitted so that middle ear and internal ear pressure can cope with outside air pressure. This hydrophobic synthetic resin lump 3 is formed by performing compressive sintering by mixing large and small particles according to use. Thus, air permeability is selected by the size of the particles and compressibility so that a decibel sound of about 1000 to 4000 is audible. Thus, an underwater sound and an external sound can be heard, and a waterproof earplug can be used for many hours without a pain of middle and external ears.