PURPOSE: To secure waterproofing by providing a closing part which is composed of plural bellows-shape protrusions and closely contacted with an opening of a terminal housing chamber to close this opening, and protruding a rear end of the closing part to be flush with the opening surface of the housing chamber or more outward than the opening surface.

CONSTITUTION: When a calking part of an electric wire terminal is calked on a side of a seal part 35, a calking connection part 33 is pulled to the inner side of a terminal housing chamber 31, however, since a rear end of a bellows-like protrusion part 47 is flush with an opening surface of the terminal housing chamber 31, a recessed part or a gap due to a stepped difference is not generated. Accordingly, even when a waterproof rubber plug 25 is displaced due to dispersion and the like of calking connection positions to the wire terminal, the bellows-like protrusion part 47 is in close contact in a state of surface contact with an inner wall 31a of the terminal housing chamber 31 and moreover, the rear end of the bellows-like protrusion part 47 is not drawn to the inside of an opening 51 of the terminal housing chamber 31, and therefore, a stepped difference part is not generated so as to inhibit accumulation of water. Consequently, infiltration of water into the terminal housing chamber 31 due to heat and vibration is never caused and waterproofing of the housing chamber 31 can be surely attained.