We report a case of Henoch-Schönlein purpura that developed after radical cystectomy. The patient was a 70-year-old man who visited our hospital with a chief complaint of asymptomatic macroscopic hematuria and was diagnosed with invasive bladder cancer. After providing one course of gemcitabine and cisplatin therapy as neoadjuvant chemotherapy, radical cystectomy was performed. Due to postoperative formation of an abscess just beneath the rectus abdominis muscle, the patient was administered antibiotic treatment. Purpura developed on postoperative day 23, and was diagnosed as Henoch-Schönlein purpura based on skin biopsy. Symptoms disappeared approximately 3 weeks later, after initiating treatment with diaphenylsulfone and prednisolone.