A piezoelectric actuator module having a multilayer structure of piezoelectric elements (3) is proposed as a piezoelectric actuator (2), wherein a different polarity of an electric voltage is alternately applied to inner electrodes which are arranged between piezoelectric layers of the piezoelectric elements (3) in the direction of the layer structure of the piezoelectric elements (3), said module having an actuator foot (4) and an actuator head (5) composed of steel and having an elastic insulation medium which surrounds at least the piezoelectric elements (3) in predefined limits. At least one annular groove (11;24) or recess (14), into which a material (12) which can be crosslinked with the insulation medium is vulcanized, is provided on the actuator foot (4) and/or on the actuator head (5), and a flexible, weldable hose (9) lies above the piezoelectric element (3) and at least above the grooves (11;24) or recesses (14) containing the material (12) as an insulation medium and is welded to the material (12) in the grooves (11) or recesses (14).