NEW MATERIAL:An optically active 2-fluorocyclopropylamine expressed by the formula (* is asymmetric carbon) and salt thereof.

EXAMPLE: (1R, 2S)-2-Fluorocyclopropylamine-hydrochloride.

USE: A medicine and production intermediate for antimicrobial compound.

PREPARATION: Cis-1-(tert. butoxycarbonylamino)-2-fluorocyclopropane is reacted with a mineral acid such as hydrochloric acid (e.g. concentrated hydrochloric acid) or sulfuric acid or trifluoroacetic acid while stirring the former compound under cooling by ice water and gradually adding the latter compound to the former compound to provide the compound expressed by the formula. When the compound expressed by the formula is an acid salt, it can be converted into free form by treating it by an ordinary method, but it may be used for next reaction directly in the form of the salt.