Hemangioma and vascular malformation are the most common benign tumors that are caused by congenitally or traumatic events. Theses tumors represent approximately 1/3~1/4 of all hemangiomas and vascular malformations in the head and neck. There are many forms of treatment for hemangioma and vascular malformation including closed observation, surgery, radiotherapy, laser therapy, steroid therapy, compression, embolization, and sclerotherapy. Ethanolamine oleate is an unsaturated fatty acid salt that has been used as a sclerosing agent because of its excellent thrombosing properties. This paper presents 1 case of intraoral multiple venous malformations treatment with 1.25% ethanolamine oleate (3.6~9.6 mg dose) intralesionally injected for 6 to 14 weeks over 2 week intervals. After the sclerotherapy, lesions almost completely disappeared without side effects. In conclusion, sclerotherapy using ethanolamine oleate is very effective against venous malformations, and sufficiently provides alternative support for surgical and other methods.