Solitary fibrous tumor of the prostate is extremely rare. Only five cases have been reported to the present. A 36-year-old man presented to our hospital complaining of difficulty in urination. Retrograde urethrography and urethroscopy demonstrated intraurethral protrusion of the left prostatic lobe and complete obstruction of prostatic urethra. Magnetic resonance imaging demonstrated the prostatic tumor with prominent intravesical protrusion. Transrectal echo-guided biopsy was performed on the supposition of leiomyosarcoma of prostate. However, the tumor was diagnosed as benign fibrous tumor, so the patient underwent transurethral resection of left prostatic lobe for the purpose of improving urinary condition, avoiding retrograde ejaculation. Histologic examination revealed a dense proliferation of spindle cells with no nuclear atypia. No mitotic figure was seen. The pathologic diagnosis was benign solitary fibrous tumor of the prostate, because the tumor was positive for CD34 and negative for alpha-smooth muscle actin and desmin by immunohistochemical study. The patient remained well without regrowth of the tumor during the last six years.