IgA pemphigus is a rare disease which is classified into two major types: subcorneal pustular dermatosis (SPD) and intraepidermal neutrophilic IgA dermatosis (IEN). The autoantigen of the SPD type was identified as desmocollin1 (Dsc1), while the antigen of the IEN type is still unknown. We report a case of IgA pemphigus possessing antibodies exclusively against desmoglein3 (Dsg3). The patient also had ulcerative colitis, clinically severe oral mucosal lesions with pustule formation, and the "sunflower-like" pustular skin lesions. Histopathology showed intraepidermal bullae with numerous neutrophils. Direct immunofluorescence showed IgA deposits in the keratinocyte cell surfaces only in the lower epidermis. Indirect immunofluorescence using normal human skin as a substrate showed circulating IgA anti-cell surface autoantibodies at a titer of 1:160. cDNA transfection test for Dsc1-3 was negative. IgA antibodies to Dsg3, but not Dsg1, were detected with IgA-ELISA for Dsgs. Addition of diaphenylsulfone (DDS) to prednisolone and cyclosporine A significantly improved the oral and skin lesions. There have been rare cases showing IgA antibodies to either Dsg1 or Dsg3. These cases can be designated as IgA pemphigus foliaceus or IgA pemphigus vulgaris, respectively, according to the autoantigens. We report here a case of IgA pemphigus vulgaris complicated by ulcerative colitis.