Resin particles containing at least binding resin and wax particles having a diameter of 30 to 600 nm are coagulated, and a resulting coagulated product is heated. Such wax particles are manufactured, for example, by way of a coarse particle preparing step, a slurry preparing step, a pulverizing step, a cooling step, and a depressurizing step. Slurry of wax coarse particles obtained by way of the coarse particle preparing step and the slurry preparing step is directed under heat and pressure through a pressure-resistant nozzle whereby the wax coarse particles are pulverized into the wax particles at the pulverizing step. The cooling step and the depressurizing step are disposed just after the pulverizing step to prevent the wax particles from coarsening.