We have developed novel solid organic materials that liquefy upon photo-irradiation. The new materials have a reversible property – they resolidify upon heating – in contrast to conventional light-sensitive polymers. This reversible switching property is induced by photoisomerization of azobenzene. Generally, isomerization of azobenzene and its derivatives readily occurs in solutions, but rarely takes place in their solid state. However, newly synthesized macrocyclic azobenzenes with flexible alkoxy chains exhibit crystal-to-isotropic phase transitions upon irradiation by light. As far as we know, this is the first report of a solid-to-liquid phase transition achieved by photoisomerization rather than heating. Our materials have potential applications to photoresists, photoresponsive adhesives, and other photoresponsive materials.