Magnetite particles (and their manufacturing method) that enable suppression of blooming caused because of their large coercive force when used as magnetic toner, exert a light environment load, and are excellent in cost. The magnetite particles contain 0.1 to 1 mass % of phosphorus, have a coercive force of 10 to 25 kA/m at a load magnetic field of 796 kA/m, and have a shape of octahedron.