We report a very rare side effect, anaphylactoid purpula, after intravesical administration of bacillus Calmette-Guerin (BCG). A 83-year-old man presented with purpura located on his bilateral lower legs. He had received transurethral resections four times for superficial bladder tumors. Intravesical therapy using BCG was performed. During the treatment course, asymptomatic purpura was suddenly seen in the lower legs after the third administration. Lymphocyte stimulation test was highly positive for BCG. He was diagnosed with anaphylactoid purpura caused by BCG. Conservative treatment was selected because there were no concomitant diseases in other organs. There have been no signs of recurrence of tumors or purpura during the one-year follow-up. However, physicians need to be cautious of anaphylactoid purpura which could lead to severe diseases, such as renal failure, gastrointestinal dysfunction and systematic arthritis.