In Sjögren syndrome, purpura is one of its various well known eruptions. Although this disease state is assumed to be based on hypergammaglobulinemia, the details of its mechanism are unknown. We experienced a case involving a female patient with primary Sjögren syndrome showing repeated purpura on the legs, and examined her blood viscosity and histopathology. This girl developed Sjögren syndrome and was admitted to our hospital at 12-years-old. She underwent steroid treatment because of aggravation of the xerosis state and prominent purpura on the legs. Hypergammaglobulinemia was improved during the course; however, purpura appeared repeatedly. Although her blood viscosity was slightly higher than normal, this had no relation to purpura and serum gamma globulin values. Skin biopsy revealed necrotizing angiitis. These results suggest that the purpura of this case was caused not only by hyperviscosity from the hypergammaglobulinemia but also involvement of vasculitis by the primary disease.