Two cases of Sjögren syndrome who developed a giant mucocele on the floor of the oral cavity are reported. Histological analysis revealed the dense infiltration of lymph-plasmacytic infiltration around the dilated salivary duct. Similar findings were observed in the biopsied specimens of the labial salivary gland which were consistent with the grade 4 score proposed by Chisholm and Mason's criteria. Mucocele is a common mucocutaneous disease of unknown etiology except for traumatic origin and Sjögren syndrome might be one of the important underlying disease which causes giant mucocele, especially in elderly female patients.