A particle size distribution creating method includes a particle size range determining step, an integrating step of integrating the frequency of appearance of particles within the particle size range determined in the particle size range determining step, a division point determining step of determining particle sizes that provide division points, using the integral of the frequency of appearance obtained in the integrating step, and a typical point determining step of determining the minimum particle size, maximum particle size and the particle sizes of the division points as typical points. This method is characterized by assuming a particle size distribution which contains particles having the particle sizes of the respective typical points and is plotted such that the frequency of appearance of the particles having the particle size of each of the typical points is equal to the integral over each of the regions defined by the typical points, and obtaining the assumed particle size distribution as a particle size distribution model.