A bone pen includes a pen which is coupled to a user's handpiece and comprises a drill section provided at an end portion thereof to drill to an alveolar bone; a cup which has an accommodating space to hold therein bone particles harvested during the drilling operation, has an outer diameter corresponding to a mesiodistal diameter of a patient's tooth targeted for treatment, and coupled to the pen so that the accommodating space can surround the drill section; and a spring which is supported at one side of the pen and elastically supports the cup with regard to the pen, wherein the drill section of the pen is positioned at a central axis line of the cup, maintained as being positioned at a mesiodistal diameter center of the tooth targeted for treatment, and guided for drilling.