Abstract: A photosynthesis inhibiting light source that emits substantially white light that does not exert an adverse influence on the human body while inhibiting/stunting the growth and propagation of photosynthetic organisms. photosynthesis inhibiting light source includes a semiconductor layer that emits near-ultraviolet light and at least one kind of fluorescent substance that emits light by being excited by the near-ultraviolet light. The near-ultraviolet light includes ultraviolet light having a light emission band in wavelengths of 300 to 380 nm and violet light having a light emission band in wavelengths of 380 to 400 nm. The mixed light of the near-ultraviolet light and light emitted by the at least one kind of fluorescent substance is substantially white.