An electrosurgical ablation apparatus for generating and emitting electromagnetic radiation energy for ablating biological tissue is disclosed. The apparatus comprises an operating unit (1), a handheld applicator unit (3) with an applicator antenna (4) and a cable connection (2) between both. The applicator antenna (4) is a dual or multi-resonant ablation antenna (41a,..41d) for transmitting microwave ablation energy at at least two different frequencies which are selected especially according to the electrical properties and dimensions of the tissue to be ablated
