A female French Bulldog was referred to Veterinary Medical Teaching Hospital, Chungbuk National University. In case, alopecia and erythema nodosum were the main complaints in a 16 months old female dog. Ventral alopecia and dorsal erythema nodosum have been presented on skin lesions for 8 months. There were no specific change with CBC and blood chemistry but plasma estrogen concentration was 68 pg/ml and cornified superficial epithelial cells were detected above $90\%$ by cytology examination of vaginal smear preparation. Ovarian cyst was detected by ultrasonography in the left ovary. Cystic diameter was $14.2 imes12.0mm$. Therefore, we diagnosed as unilateral multiple follicular cysts. The dog was treated with GnRH $50{mu}g$ injection by intramuscularly Cyst size was decreased $7.3 imes7.2mm$ after 7 days GnRH treatment and disappeared after 14 days GnRH treatment. Also dermatitis by unilateral multiple follicular cysts were recovered after 21 days GnRH treatment.