When conventional photo-reactive compounds are to be liquefied with the application of light, liquefaction thereof is time-consuming due to poor sensitivity to ultraviolet light. In the case of conventional photo-reactive compounds, disadvantageously, light does not penetrate through layers to be adhered to each other when such layers are thick. Thus, peeling is not sufficiently performed. Accordingly, it is an object of the present invention to overcome such drawbacks of conventional photo-reactive compounds and provide a photo-reactive adhesive agent exhibiting high sensitivity to light for fluidization and capable of easy peeling. This invention provides a photo-reactive pressure-sensitive adhesive agent comprising, as a main component, a polymeric compound with a weight average molecular weight of 3,000 to 800,000 represented by General Formula (1): wherein A represents a block polymer of monomers represented by Formula (2) below with a molecular weight of 1,000 to 100,000; and B represents a block polymer with a molecular weight of 1,000 to 400,000 having a glass transition point and a melting point of 20° C. or lower, which is liquid or plastically deformable at room temperature, provided that B does not absorb light of a wavelength range of 350 to 600 nm by itself: wherein R1 represents a group having an azobenzene structure represented by Formula (3) below; n is an integer of 2 to 18; m is an integer of 0 to 16; and R2 represents hydrogen or a methyl group.