A magnetic encoder includes a multipolar magnet, having magnetic poles formed therein so as to alternate with each other in a direction circumferentially thereof, and a core metal supporting the multipolar magnet. The multipolar magnet is prepared from a sintered element formed by sintering a powdery mixture of a magnetic powder and a non-magnetic metallic powder. This multipolar magnet is fixed to the core metal to form a unitary component made up of the sintered element and the core metal. The unitary component is subjected to a surface treatment for anticorrosion.