Mercury is one of the most frequently used heavy metal in dental clinic. Mercury poisoning rises up when someone is exposed to mercury chronically. In 1818, Amalgam was used for dental restorative procedure, and after then study about mercury toxicity has begun. Clinical signs of mercury toxicity in oral & maxillofacial area were increases of salivation, metallic taste, swelling and pain of tongue, redness and ulceration of oral mucosa, and increased mobility and loss of teeth. After we injected mercury($HgCl_{2}$) into intraperitoneum of rat, studied about histopathological changes of submandibular gland cell. Experimental group was divided into two groups by amount of mercury. (Group 1 was 0.5mg/Kg of mercury injection, group 2 was 1.0mg/Kg of mercury injection.) 1. After 3days of intraperitoneal injection, black granules were observed at macrophage cell in both group. In group 2, author found hyperchromatism of nucleus, and vacuolization of cellular matrix and nucleus of acinar cell. 2. After 1week of intraperitoneal injection, author found severe vacuolization of nucleus and cellular matrix, and irregular granules around nuclear membrane at mucous cell and serous cell in both group. Vacuolization of nucleus and cellular matrix was seen at duct cell in group 2. 3. After 2weeks of intraperitoneal injection, author could found severe vacuolization of cellular matrix, and sometimes nucleus was positioned in central area of cellular matrix at mucous and serous cell in both group. Vacuolization of nucleus and cellular matrix was found at vascular endothelial cell in group 2. 4. After 4weeks of intraperitoneal injection, destruction and distortion of gland cells were distinct. Vacuolization and destruction of nucleus and cellular matrix was found at duct cell in group 2. After intraperitoneal injection of mercury, we found equanimity of mercury and destruction of cellular matrix at serous cell, mucous cell, and duct cell of submandibular gland. So, we thought that metallic taste of mercury poisoning patient would be due to excretion of saliva containing mercury.