Abstract: A mark forming apparatus including a guide needle for forming a mark, a positioning mechanism, a solution supply device, and a heating unit is disclosed. The positioning mechanism is used for positioning the guide needle above a fault location of a semiconductor device. The solution supply device supplies a solution containing a coloring agent and a volatile solvent to the fault location until it touches a tip of the guide needle. The heating unit evaporates the volatile solvent to form a mark consisting of the coloring agent surrounding the fault location.