Provided are a method for producing 3-methylglutaraldehyde in a good yield under a mild condition and a novel acetal compound which is useful for carrying out the foregoing method. The method is a production method of 3-methylglutaraldehyde including a step of hydrolyzing a compound represented by the following general formula (1): wherein R1 and R2 each independently represent an alkyl group having 1 to 6 carbon atoms, or are mutually coupled to represent an alkylene group having 2 to 6 carbon atoms.