The present disclosure discloses a method and a device for continuously synthesizing cyclopropane compounds. The method includes the following steps: continuously performing a synthetic reaction of a diazomethane precursor in a first reactor, the reaction product of the first reactor flowing into a separator for stratification, the organic phase obtained by stratification overflowing into a second reactor, continuously consuming the diazomethane precursor in a second reactor to prepare diazomethane and performing an electron-rich monoolefin cyclopropanation reaction in situ so as to obtain the cyclopropane compound.