A
reaction product and an
imide compound can be separated from a reaction mixture obtained by reacting a substrate in the presence of the
imide compound having an
imide unit represented by the following formula (1): wherein X represents an
oxygen atom, a hydroxyl group or an acyloxy group by (A1) a
solvent-
crystallization step for crystallizing the imide compound with at least one
solvent selected from the group consisting of a
hydrocarbon, a chain
ether and water, (A2) a cooling-
crystallization step for crystallizing the
reaction product by cooling, or (B) an extraction step for distributing the
reaction product into a phase of a water-insoluble
solvent and the imide compound into a phase of an aqueous solvent, respectively by using the aqueous solvent containing at least water and the water-insoluble solvent separable from the aqueous solvent. Further, the imide compound and the
metal catalyst can be separated from a mixture containing the imide compound and the
metal catalyst by (C) a solvent-
crystallization step for crystallizing the imide compound by using a solvent for crystallization, (D) an absorption step for absorbing the
metal catalyst by an absorption treatment, or (E) an extraction step for distributing the imide compound into a phase of a water-insoluble solvent and the
metal catalyst into a phase of an aqueous solvent, respectively by using the aqueous solvent containing at least water and the water-insoluble solvent separable from the aqueous solvent.