We introduce FeCo‐BaF and FeCo‐SiN nanogranular films exhibiting giant Faraday effect. These films have a nanocomposite structure, in which nanometer‐sized FeCo ferromagnetic granules are dispersed in BaF2 or Si3N4 matrix. FeCo‐BaF film has a good figure of merit of Faraday effect from the crystalized BaF2 matrix. FeCo‐SiN film has a large refraction index from the nature of Si3N4 matrix. These properties contribute to the practical application of nanogranular films to optical devices. [ABSTRACT FROM AUTHOR]