PURPOSE: To simplify a device and to prevent a leakage of water from a watertight tubular body by providing an intermediate tubular body between a cable and the watertight tubular body and by covering parts between the intermediate tubular body and the watertight tubular body and between the intermediate tubular body and the cable with heat-shrinkable tubes.

CONSTITUTION: A watertight structure is constructed of at least one intermediate tubular body 4 provided between the end parts of a watertight tubular body 2a and a cable 1a and of heat-shrinkable tubes 3 provided for covering parts between the intermediate tubular body 4 and the watertight tubular body 2 and between the intermediate tubular body 4 and the cable 1a. According to this constitution, a difference in the outside diameter between the cable 1a and the watertight tubular body 2a is reduced, a weakness due to the use of the heat-shrinkable tubes is thereby prevented, and the watertight structure of the cable 1a of which the fitting is simplified and which enables prevention of a leakage of water from the watertight tubular body 2a can be obtained.