To provide a release wire of a remote control type drain plug device, capable of suppressing expansion and contraction of an outer tube due to change in temperature and preventing metal wires arranged in an outer tube from popping out when the outer tube contracts.

An outer tube 2 is divided into an inner layer 3 and an outer layer 4, and has metal wires 5 of mesh shape between the inner layer 3 and the outer layer 4. The outer tube 2 is provided with a hard material 7 at one end thereof. When heat or the like is added to the outer tube 2 from the exterior, the metal wires 5 in the inside of the outer tube 2 suppresses the contraction of the outer tube 2, and the hard material 7 restricts popping out of the metal wires 5 even when the outer tube 2 tends to contract with a force exceeding the suppression force of the metal wires 5.