The present invention relates to a magnetic carrier for an electrophotographic developer comprising spherical composite particles comprising spherical composite core particles comprising at least ferromagnetic iron oxide fine particles and a cured phenol resin and having an average particle diameter of 1 to 100 µm, and a melamine resin coating layer formed on the respective core particles, wherein a ratio of R 100 to R 300 (R 100 /R 300 ) in which R 100 is an electric resistance value as measured when applying a voltage of 100 V to the magnetic carrier; and R 300 is an electric resistance value as measured when applying a voltage of 300 V to the magnetic carrier, is controlled to lie within the range of 1 to 50. The magnetic carrier according to the present invention is capable of maintaining an adequate electric resistance value upon development, providing images having an excellent image quality, exhibiting a good durability, obtaining a good reproducibility of uniform solid image portions having a high image density, and keeping high quality images having an excellent gradation for a long period of time.