Lichen planus (LP) is a chronic inflammatory disorder involving the skin or mucous membranes. Previous studies have demonstrated that some LP patients showed positive enzyme-linked immunosorbent assay (ELISA) for desmoglein (DSG) antibodies. We report a case with intractable painful oral lesions. ELISA indices for DSG1 and 3 antibodies were increased by 49 and 36, respectively. Histopathological analysis revealed irregular acanthosis and band-like infiltration of lymphocytes at the dermal–epidermal interface. Direct immunofluorescence revealed negative deposits of immunoglobulin G and C3 in intracellular spaces of the epidermis. Indirect immunofluorescence of normal skin also did not detect any antibodies. Consequently, we made a final diagnosis of oral LP. The previous two LP cases with positive ELISA for DSG antibodies and our case manifested the erosive form, the most advanced oral LP. Therefore, it is a possibility that severe damage of keratinocytes may induce generation of DSG antibodies. However, negative results of immunofluorescence and no relation between disease severity and titers of antibodies make the possibility unlikely. We should measure titers of DSG antibodies in LP patients and accumulate data to establish a valid conclusion.