The National Institute of Information and Communications Technology has successfully developed a highly efficient optical modulator using organic electro-optic polymer (hereinafter referred to as EO polymer) for visible light. Conventional EO polymer optical modulators could operate in near-infrared light (wavelength 1,550 nm, etc.), but they couldn't be used for visible light (wavelength 380 nm to 780 nm) because of the large absorption loss. NICT has developed an EO polymer which experiences small absorption loss in visible light and has the large electro-optic coefficient required for the optical modulator. We fabricated an optical modulator using this EO polymer by microfabrication technology and operated the optical modulator in visible light (red, wavelength 640 nm). The demonstrated optical modulator for visible light is smaller and more efficient than the conventional EO polymer optical modulator for near-infrared light.