The utility model provides a mercury removing device of a mercury-containing rock core, which is applied to mercury removing treatment of an oil field laboratory rock core. The mercury removing device is characterized in that a quartz tube is arranged in a tubular heating furnace; the mercury-containing rock core is placed in the quartz tube; the quartz tube is circular and one end of the quartz tube is provided with an opening; the opening end of the quartz tube is connected with a rubber pipe; the other end of the rubber pipe is connected with an air inlet of the middle part of a condenser; a condensed water inlet pipe of the condenser is connected with a tap water pipe; a water outlet pipe of the condenser is communicated with a sewer by using the rubber pipe; a collection bottle is connected with a collection opening at the lower end of the condenser; an upper end air outlet of the condenser is connected with a second rubber pipe; and the other end of the second rubber pipe is connected with an air inlet of a circulating water type vacuum pump. The mercury removing device has the effects that the mercury-free treatment of the mercury-containing rock core is realized; and the treated rock core can be treated as a normal rock core and the collected mercury is reutilized.