A visible laser oscillation has been achieved on the electron storage ring TERAS at 598 nm using a 1.47 m optical klystron. TERAS was operated in a three-bunch mode at a beam energy of 231 MeV with a beam current ranging from 3 to 10 mA per bunch. Coherent phase oscillations of the beam bunches were successfully suppressed by controlling a second harmonic RF cavity (Landau cavity) whose driving frequency is 343.24 MHz. The laser linewidth was observed to be 0.26 nm, including the detector resolution (0.21 nm). The spectral intensity was about 10(4) times as large as that of the spontaneous emission. The peak laser power of the microtemporal pulse is roughly measured to be 10 mW at beam current 4 mA/bunch.