Abstract: The present invention provides a magnetic carrier for an electrophotographic developer which has an excellent durability and a stable charging property and is free from occurrence of spent toner thereonto, and a two-component system developer comprising the magnetic carrier for an electrophotographic developer and a toner. The present invention relates to a core material of a magnetic carrier for an electrophotographic developer comprising spherical composite particles comprising at least ferromagnetic iron oxide fine particles and a cured phenol resin and having an average particle diameter of 1 to 100 ?m, a resin index of the spherical composite particles being within the range of 35 to 80%, and a magnetic carrier obtained by coating a surface of respective particles of the magnetic carrier core material with a resin.