A testing device utilized in a testing apparatus includes a top guiding board having top penetrating openings, a bottom guiding board disposed at one side of the top guiding board and having bottom penetrating openings, and elastic contact structures disposed between the top guiding board and the bottom guiding board. A testing device offset (represented by d2) exists between the top guiding board and the bottom guiding board. Each elastic contact structure has a tip section, a body section, and a tail section in sequence. The elastic contact structures pass through the top penetrating openings and the bottom penetrating openings respectively Each elastic contact structure has an elastic contact structure offset between the tip section and the tail section. Each elastic contact structure has a target elastic contact structure offset (represented by d1), in which d1 and d2 satisfy the following equation: d2=d1±50˜200 μm.