To provide a polyurethane prepolymer whereby a pressure-sensitive adhesive having excellent moisture permeability and also having both low adhesion to skin and high adhesion to a substrate can be obtained, a pressure-sensitive adhesive, an adhesive skin patch, a pressure-sensitive adhesive tape, a wearable device and a wearable device kit.;A hydroxy group-terminated polyurethane prepolymer which is obtained by reacting an oxyalkylene polymer A having an average number of hydroxy groups per molecule of from 2.1 to 3, an oxyalkylene polymer B having one hydroxy group per molecule, and a diisocyanate compound, wherein the number average molecular weight of the oxyalkylene polymer B is at least 5,000, and the content of ethylene oxide units in the hydroxy group-terminated polyurethane prepolymer is more than 10 mass%, a pressure-sensitive adhesive, an adhesive skin patch, a pressure-sensitive adhesive tape, a wearable device and a wearable device kit.
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