The present invention is directed to a magnetic seal device comprising a magnetic sleeve (7) having a cylindrical body (71) and fitting on an outer peripheral surface of a rotatable shaft (3), a ring shaped magnet (8) being arranged radially outwardly from an outer peripheral surface of the magnetic sleeve (7) with a gap, and forming a magnetic circuit between the outer peripheral surface of the magnetic sleeve (7) and the ring shaped magnet (8), and a magnetic fluid (10) being maintained at the gap. The magnetic sleeve (7) includes a groove (72) arranged circumferentially around the outer peripheral surface of the magnetic sleeve (7), and a flange (73) extending radially outwardly from and circumferentially around the outer peripheral surface of the magnetic sleeve (7), wherein the flange has a diameter that is larger than a diameter of the outer peripheral surface of the magnetic sleeve (7). The invention is further directed to a fishing reel comprising such a magnetic sleeve.
