PURPOSE: To provide a coupler surely sealed from outdoor air, especially humidity, for the branching positions or connection positions of an electric cable, especially a light wave conductor cable.

CONSTITUTION: This coupler is provided with a heat shrinkable sleeve 11, composed of a synthetic material and provided with vertical slits 12, 13, 14 and 15, terminal part members 4 and 5 provided with a spread open part, a pass- through opening, a bag hole 17 and a molded material 16 laminated by a hot- melting adhesive material.