A laser frequency stabilizing apparatus stabilizes an oscillation frequency of laser light by varying a resonator length on the basis of a saturated absorption line included in an optical output signal. The optical output signal is obtained by irradiating an absorption cell with the laser light. The laser frequency stabilizing apparatus includes: a light detecting section for detecting the optical output signal; a differential signal detecting section for detecting a differential signal of the optical light signal; an actuator for varying the resonator length; a drive section for driving the actuator; and a control section for controlling the drive section on the basis of the differential signal. The control section determines saturated absorption lines on the basis of an output of the differential signal, selects a specific saturated absorption line on the basis of the number of determined saturated absorption lines and a combination of the determined saturated absorption lines, and stabilizes the oscillation frequency of the laser light at the specific saturated absorption line.