To provide a method for setting a condition under which all materials of analogous structure are resolved at once when resolving a mixture containing a plurality of materials of analogous structure having a similar chemical structure by a capillary electrophoresis method.

There are provided a process (1) where the pKa of each material of analogous structure contained in the mixture is acquired, and based on the information of pKa, the pH range of a migration solution suitable for resolving the material of analogous structure is set, a process (2) where, while the pH range of the migration solution acquired in the process (1) is applied, the appropriate range is partially determined by an implementation factor examination for each of two or more separation parameters, and a process (3) where at least one parameter among the separation parameters used in the process (2) is optimized by a factor examination.