A sensor includes: a base layer; first and second conduction paths supported by the base layer; a first adhesive layer covering a first portion of the first conduction path; a second adhesive layer covering the second conduction path; an insulation sheet including: a first protecting portion covering the second adhesive laver; a second protecting portion disposed between a second portion of the first conduction path, and a part of the second conduction path; and a third protecting portion covering the first adhesive layer; a detecting section; a wireless transmitter; and a power source. When the insulation sheet is peeled off, the second portion of the first conduction path, and the part of the second conduction path are caused to be in contact with each other, and an electric power is supplied from the power source to the detecting section and the wireless transmitter.