A testing head for testing the working of a device under test comprises a plurality of contact probes, each contact probe having a rod-like body of a predetermined length that extends between a first end and a second end and being housed in respective guide holes made in at least one plate-like lower guide and one plate-like upper guide that are parallel to each other and spaced apart by a bending zone. Suitably, at least one of the lower guide and upper guide is equipped with at least one recessed portion formed at a plurality of those guide holes and realizing lowered portions thereof adapted to reduce a thickness of the plurality of those guide holes.