In order to make it possible to produce 6-methylheptan-2-one, which is useful as a material for synthesizing isophytol or as a material for synthesizing fragrances such as tetrahydrolinalool and dihydrogeraniol, efficiently and in an industrially simple manner, isovaleral and acetone are subjected to aldol condensation in the presence of a basic substance to form a condensate which contains 4-hydroxy-6-methylheptan-2-one, and then the condensate is subjected to hydrogenation reaction under a dehydration condition to obtain the 6-methylheptan-2-one.