By a method for producing a diamine comprising the step of purifying a diamine from an aqueous solution containing a diamine salt, the method comprising a step of adding an alkaline substance to the aqueous solution and then filtering the resulting solution by allowing the solution to pass through a nanofiltration membrane to remove the salt, thereby obtaining an aqueous diamine solution, a diamine suitable as a raw material for a polyamide can be obtained by a simpler operation than by a conventional extraction operation with an organic solvent.
