A purge plug containing a refractory material is configured to be inserted in the bottom of a ladle for introducing purging gas through a heat of molten metal in the ladle. The purge plug houses a retention chamber for holding the lead content of lead-containing molten steel alloys that leaches into, or infiltrates into, the purge plug. The purging gas supply tube is provided with a portion that protrudes into the retention chamber, thereby preventing the lead content of lead-containing molten steel alloys from entering and blocking the purging gas supply tube.