A piezo-electric motor of the stationary wave tape comprises a stator including piezo-electric excitation means capable of inducing a vibratory motion in the stator, a rotor mounted for rotation relative to the stator, the rotor including a body on which are assembled flexion tabs forming transmission means arranged to transmit the vibratory motion of the stator to the rotor and to rotationally drive such rotor, said flexion tabs following a displacement path relative to the stator, and an angular position detector of the rotor. The motor is characterised in that the detector is arranged near and in line with the displacement path, and in that said detector is formed by one or several piezo-electric sensors allowing to track the passage of the tabs. The motor is particularly suitable for timepieces.