A high‐power, frequency‐stabilized laser source is required for an atomic force microscope which uses interferometric techniques to obtain distance measurements with picometer resolution. For this purpose, the oscillation frequency of a 10 mW multimode He‐Ne laser was stabilized using a new technique. Optical interaction between the longitudinal modes synthesizes intermode beats. Frequency of the intermode beat signal changes periodically with respect to cavity thermal expansion. This phenomenon is explained by the concept of ‘‘frequency pulling.’’ The secondary beats synthesized by the interaction between the intermode beat signals also change due to frequency pulling. The relation between the secondary beat of an intermode beat frequency and the laser cavity length is utilized for the stabilization of laser frequency. The change in the frequency of the secondary intermode beat is employed as the feedback signal to control the length of the cavity of the laser. To detect the frequency change in the secondary beat signal, a simple microwave electronics circuit was designed. An excellent frequency stability (instability: ±2 parts in 108) and high‐power laser output were obtained successfully using this simple technique.