PURPOSE: To provide a method for treating dried aspartame having extremely high qualities and a high rate of dissolution, containing a very small amount of a substance requiring retreatment.

CONSTITUTION: In this method for treating a dried aspartame, particles having <50 μm are removed from an aspartame having a particle size distribution composed of ≥5 wt.% of particles smaller than 20 μm and ≥10 wt.% of particles larger than 400 μm by a first classification process using an air flow in combination and, in a second classification process, the aspartame after the first classification process is passed through a sieve having a classification diameter of 150-250 μm, smaller particles are recovered as a first product and larger particles are recovered as a second product or the larger particles are optionally passed through a sieve having 400-1,000 μm classification diameter and the prepared smaller particles are recovered as a second product to give the objective method for producing a dried aspartame.