A laser-frequency stabilizer includes: a light detector that converts a laser beam passing through an iodine cell to an optical output signal, an actuator that changes a resonator length in accordance with a received output voltage, and a control unit that controls the output voltage applied to the actuator. The control unit searches for a target saturated absorption line based on the optical output signal and, when the output voltage when the target saturated absorption line is found is within a normal voltage range that is predetermined corresponding to the target saturated absorption line, locks a oscillation frequency of the laser beam to the target saturated absorption line.