Disclosed is a method for producing an optically active 3-methylcyclopentadecan-1-one which is characterized in that 2-cyclopentadecen-1-one is subjected to a 1,4-conjugate addition reaction of a methyl group by using a methylated organic metal in the presence of a copper catalyst, an enol anion scavenger and a specific optically active phosphoramidite for obtaining an optically active 3-methyl-1-cyclopentadecene derivative, and then the thus-obtained 3-methyl-1-cyclopentadecene derivative is subjected to a solvolysis.