Disclosed is a method for producing 4,6-dialkoxy-2-cyanomethylpyrimidine and also disclosed is a synthetic intermediate thereof. More specifically disclosed is a method for producing 4,6-dialkoxy-2-cyanomethylpyrimidine represented by general formula (2) (wherein R represents an alkyl group), comprising reacting a t-butyl cyanoacetate derivative represented by general formula (1) (wherein R has the same meaning as described above) in the presence of an acid, and also disclosed is a t-butyl cyanoacetate derivative represented by general formula (1) (wherein R represents an alkylgroup).