Malachite green derivatives bearing methyl, methoxy, hydroxyl and amino group were synthesized by the condensation reaction of N,N-dimethylanilin with substituted benzaldehydes. The yield of malachite green derivatives increased with addition of urea as an additive. Antimicrobial and antifungal activities of those compounds were evaluated in terms of minimum inhibitory concentration by the dilution method. It was observed that the antimicrobial and antifungal activity of the malacite green derivatives bearing electron-releasing substituents was stronger than that of the unsubstituted malachite green. From this result, it was concluded that the antimicrobial and antifungal activity of malachite green derivatives has a direct relationship with the electronic effect of the substituents.