Provided is a high-speed ring optical modulator based on a silicon semiconductor, having increased optical modulation speed. The high-speed ring optical modulator includes a ring optical waveguide including a portion in which the refractive index varies, that is, a refractive index variation portion, and an optical waveguide having a constant refractive index. The refractive index variation portion comprises a bipolar transistor. Thus carriers can be supplied to and discharged from the refractive index variation portion, through which light is transmitted, at high speed, and thus the optical modulation speed can be increased.