We reported one case of penile angiosarcoma in a 49-year-old patient who had been misdiagnosed as syphilis. Based on our experience, we suggest that if sexually transmitted diseases and Peyronie's disease can be ruled out, diagnosis of the penile angiosarcoma be warranted if unexplained rash, ulceration on the penis, and induration in corpus cavernosum are observed. It should be noted that if the anti-inflammatory or anti-viral treatment is prescribed for some time but the lesion does not disappear or even gets worse, the penile angiosarcoma should be suspected and penile biopsy is necessary.