PURPOSE: To provide a water-tight insulated electric wire completely filled with a water-tight mixture in clearances among element wires.

CONSTITUTION: A twisted wire conductor 5 is composed of a first layer 3 provided with one piece of element wire 1 in the center thereof, and a second layer 4 with numerous element wires 2 disposed coaxially with the first layer 3. In a water-tight insulated electric wire filled with a water-tight mixture 6 in clearances 8 formed among the element wires 1, 2 constituting the layers 3, 4 of the twisted wire conductor 5, a groove 10 is formed in the longitudinal direction of the element wire 2 of the second layer 4. The water-tight mixture 6 is filled in the clearance 8 through a communicating passage defined by the groove 10.