We encountered the rare case of a 50-year-old woman who developed rheumatoid arthritis (RA) while suffering from Takayasu's arteritis of arch vessel type. prednisolone (PSL) therapy was continued at a maintenance dose of 7.5 mg due to recurring inflammation. She was affected with RA for 7 years after Takayasu's arteritis. Disease-modifying antirheumatic drugs (DMARDs) were unusable because of side effects. In the summer of 2005, RA activity increased, and treatment with tacrolimus hydrate at 1.5 mg was started; thereafter, the activity of RA and Takayasu's arteritis was relieved, especially MRA findings. We report that therapy with tacrolimus hydrate markedly relieved two disorders, and review the literature.