A ring−shaped elastic material (3) as a magnetic member for a revolution detector containing a hydrogenated nitrile rubber as a base material and strontium ferrite as a magnetism imparting component, wherein the magnetic material comprises the strontium ferrite in an amount of 80 to 90 wt %. The strontium ferrite content of 90 wt % or less allows no cracks in the thermal shock test (the thermal shock between −40˚C and 150˚C), which leads to the endurance to a severe temperature condition in use, and the strontium ferrite content of 80 wt % or more allows the ensurement of a magnetic flux density required for a revolution detector. The magnetic member for a revolution detector not only can endure a severe temperature condition in use, but also exhibits stable magnetic characteristics.
