There is provided a method of manufacturing a magnetic particle, which comprises: the alloy particle preparation step of preparing an alloy particle capable of forming a CuAu type or Cu3Au type hard magnetic ordered alloy phase and the magnetic particle formation step; wherein in the alloy preparation formation step, by using a mixing and reaction device which has a stirring vane rotating at a high speed in the interior of a mixer, a plurality of kinds of solutions for preparing the alloy particle are supplied to the interior of the mixer, where the plurality of kinds of solutions L1 and L2 are mixed together and caused to react with each other by a liquid phase process, and at the same time the plurality of kinds of solutions are mixed together and caused to react with each other so that the peripheral speed in a leading end portion of the stirring vane is not less than 10 m/second.