To develope an alternative method for manufacturing an unsaturated and methyl-substituted macrocyclic ketone or lactone which is interest in view of aromatic odor from a corresponding ketolactone or diketone.

The new unsaturated and methyl-substituted macrocyclic keton or lactone is manufactured by subjecting the corresponding ketolactone or diketone to a Grignard reaction using a methyl magnesium halide and a subsequent acid dehydration reaction. Since the manufacturing method does not use a Wittig reaction or a reaction with a large excess of methyl lithium, a manufacturing cost is reduced and also the operation on an industrial scale is facilitated.