Abstract: The invention discloses an outside type mechanical seal device disposing the mechanical seal main body at the atmospheric side so as to stop leak of shaft seal of rotary shaft, comprising an annular stopper ring fixed on the rotary shaft by a setbolt, an annular flange bolted to the fixed side, plural protrusions formed integrally at positions confronting the stopper ring outer circumference in the flange at specified intervals to the outer circumference, spacers interposed between the inside of the protrusions and the outer circumference of the stopper ring, and cap bolts detachably driven into the stopper ring through the protrusions and spacers from outside the protrusions, wherein the axial center of rotary shaft of the stopper ring disposed on the rotary shaft is securely positioned in the radial direction and thrust direction, and the entire outside type mechanical seal composed of multiple parts is formed into one integral unit, thereby facilitating the assembling performance.