We have designed and developed a light-source system to support advanced experiments for plant light-response studies. The light-source system consists of light-emitting diodes (LEDs) of five types: violet, blue, orange-red, red, and far-red (peak wavelengths, λp: 405, 460, 630, 660, and 735 nm). The light-source system can produce light with different compositions of the five wavelength ranges, and can provide photosynthetic photon flux densities (PPFDs) of 488 μmol m-2 s-1 for an area of 0.18 m2 at a distance of 173 mm below the LEDs. This is sufficient for the cultivation of almost all leafy vegetables and other plants that might be produced under artificial light in commercial plant factories. This report provides a technical description of the light-source system and the results of quantification tests.