The invention provides a puncturing guide (1, 16) for guiding a puncturing needle into a target site within the body of a patient. The puncturing guide (1, 16) comprises a base plate (2, 17), a needle guide (3, 18), a retainer (4, 19) for securing the needle guide (3, 18) to the base plate (2, 17), a first segment (7, 20) of a first semi-sphere, a second segment (8, 21) of a second semi-sphere, and a needle guide (3, 18) attached to the second segment (8, 21). During a positioning operation, the second segment (8, 21) slides on the first segment (7, 20), so that the needle guide (3, 18) is movable around the center of the first semi-sphere, which is in level with the underside of the base plate (2, 17), thereby providing the possibility to position the tip of a puncturing needle at a puncturing point on the patient's skin and then, in a separate operation, set the entrance angle of the puncturing needle without changing its entrance point.