The present invention has for its object to provide a method for producing an L-allysine acetal which involves a fewer steps and is efficient. This invention relates to method for producing an L-allysine acetal which comprises; converting a D,L-allysine acetal of the following general formula (1) (wherein R1 and R2 are the same or different, and each of them represents an alkyl group having 1 to 8 carbon atoms, or they combinedly form a ring and represent an alkylene group having 2 to 8 carbon atoms) to a mixture of a 2-oxo-6,6-dialkoxyhexanoic acid of the following general formula (2) (wherein R1 and R2 are as defined above) and an L-allysine acetal of the following general formula (3) (wherein R1 and R2 are as defined above) by reacting in the presence of an enzyme capable of stereoselective oxidative deamination of D-amino acids and; isolating said L-allysine acetal after said converting.