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