The basic performance of pulse-operated dye-doped plastic optical fiber (DPOF) for photodynamic diagnosis (PDD) and photodynamic therapy (PDT) and the photochemical property of photosensitizer are demonstrated. As the dopant in DPOF, Rhodamine 6G, which has a high optical gain of at the latter half of 500 nm, is prepared. Output power from the R6G-doped DPOF is irradiated onto the photosensitizer (zinc (II)5, 10, 15, 20-tetraphenyl porphyrin: ZTP), and fluorescence from the ZTP is observed. Generation of superoxide, which is a form of active oxygen, is confirmed by the method of photochemical reaction. In addition, the possibility of a medical-optical device DPOF is discussed.