A reversible isothermal phase transition between the liquid and solid states in response to light irradiation was achieved in side chain-type azobenzene polymers. These materials can be used as adhesives that are detachable without applying any mechanical and thermal stress but also repeatedly reworkable because of their photoinduced liquefaction and solidification properties. The adhesive strength to glass plates was more than 3 MPa in single lap shear tests. This value is three times higher than previously reported and is sufficiently strong for glass substrates.