The invention discloses a lead replacing device of a propelling pencil. The lead replacing device of the propelling pencil comprises a lead storage tube used for storing bullet leads. A lead discharging head assembly used for keeping the bullet leads in the lead storage tube is arranged at one end of the lead storage tube. The lead discharging head assembly is connected with a one-way lead feeding channel of the propelling pencil in an inserted and matched mode, so that a bidirectional-opening lead feeding structure which opens a necking assembly in the radial direction is formed, wherein an outlet of the lead storage tube is opened through the lead feeding structure. According to the lead replacing device of the propelling pencil, the lead discharging head assembly which is matched with the one-way lead feeding channel of the propelling pencil and allows one-way lead feeding is arranged on the lead storage tube, the purpose that the lead is replaced conveniently without contact with the lead can be achieved just by enabling the lead discharging head assembly to be matched with the one-way lead feeding channel of the propelling pencil, and lead replacement is safer and more sanitary.