There are provided magnetic iron oxide particles having an average particle diameter (Dp 50 ) of primary particles of 0.05 to 0.3 µm, an average particle diameter (Da 50 ) of secondary particles of 0.055 to 0.9 µm, and a ratio of the average particle diameter (Da 50 ) of the secondary particles to the average particle diameter (Dp 50 ) of the secondary particles (Da 50 / Dp 50 ) of 1.1 to 3.0, as well as a magnetic toner containing the magnetic iron oxide particles. These magnetic iron oxide particles are in the form of small agglomerated particles and exhibit an excellent dispersibility. A magnetic toner incorporating the magnetic iron oxide particles exhibits excellent electrification stability.