This paper proposes a new inductance-identification method for synchronous motors including permanent-magnet synchronous motor (PMSM), synchronous reluctance motor, and PMSM with double three-phase windings. The proposed method is based on the generalized flux estimation method instead of the adaptive parameter identification methods, and has the following features: the inductance is identified online during the rotating operation; it uses the so-called “D-filter” and can reduce the effects of noise and harmonics on the identified values; it can be applied to motors with magnetic saturation and dq-axis flux coupling characteristics; and it can be applied in the transient state as well as in the steady state. The propagation of errors due to other parameters into the identified inductance is analyzed. The effectiveness and usefulness of the proposed method are verified through extensive simulations.