The present invention provides a process for producing (Z)-1-phenyl-1-diethylaminocarbonyl-2-aminomethylcyclopropane or hydrochloride thereof, which comprises a step of reacting (Z)-1-phenyl-1-diethylaminocarbonyl-2-phthalimidomethylcyclopropane by contacting said compound with an aqueous methylamine solution having a concentration of from 1 to 25% by weight to obtain (Z)-1-phenyl-1-diethylaminocarbonyl-2-aminomethylcyclopropane.