Bacterial infection of canine atopic dermatitis is largely caused by Staphylococcus intermedius and may be a superficial or deep pyoderma. The Purpose of this study was to identify the major proteins of S. intermedius cell surface components in humoral immune response of atopic dermatitis dog. Sera samples were obtained from dogs with atopic dermatitis and superficial pyoderma referred to the Veterinary Medical Teaching Hospital, Konkuk University. An isolate of S. intermedius from a clinical case of canine atopic dermatitis was cultured in brain heart infusion broth overnight at $37^{circ}C$ in aerobic conditions on an orbital shaker. Following culture, Staphylococci were harvested by centrifugation, washed in PBS, and resuspended in PBS containing lysostaphin. The soluble components were separated by centrifugation and were collected. The soluble extract of S. intermedius was separated by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE). The proteins were electrophoretically transferred onto nitrocellulose membrane. Western blotting for the specificity of serum IgG antistaphylococcal antibody was performed with anti-dog-IgG and sera obtained from an atopic dermatitis case and a normal dog. The molecular masses of four major proteins of S. intermedius recognized by serum obtained from an atopic dermatitis case were 18, 31, 75, and 110 kDa as determined by Western blot analysis. The present study indicates that most dogs of S. intermedius infection with atopic dermatitis could have a significant humoral immune response to bacterial proteins of the causative organism.