The full hyperfine components of theR(127) line in the 11‐5 band and the 10 components of theP(33) line in the 6‐3 band of theB←Xelectronic transition of127I2were observed by the saturated absorption spectroscopy using a complex resonator He‐Ne laser. The frequency of the laser was locked to each component and the frequency separations of the components were precisely measured. The hyperfine structure of theR(127) line was compared with a model which included both a nuclear electric quadrupole and magnetic hyperfine interactions.