A portable device, which performs wireless communication with a communication peer, includes a battery, which powers an electronic component, and a case, which accommodates the electronic component and battery. The case includes a battery compartment having an opening. An elastic waterproof seal surrounds the opening. A battery lid, which covers the opening, is formed integrally with the waterproof seal and coupled to the case in a direction perpendicular to a radial direction of the waterproof seal. A rim around the opening of the battery compartment pushes the waterproof seal when coupling the battery lid to the case thereby elastically deforming the waterproof seal in an inward radial direction. The waterproof seal, when elastically deformed, keeps the battery lid coupled to the case and seals the battery lid and case in a liquid-tight state.