We propose a photobase generator (PBG) that liberates two bases by absorbing one photon. Phototriggered decarboxylation proceeds first to generate one base, and subsequently the unstable reaction intermediate is thermally decarboxylated to generate another base. It was found that the photosensitivity of poly(glycidyl methacrylate) films containing the PBG is much higher than that of films containing a conventional PBG that generates one base by absorbing one photon.