The present invention relates to a process for preparing (Z)-7-tetradecen-2-one of the following formula (5), the process comprising the steps of converting a (Z)-1-halo-4-undecene compound (1) of the following general formula (1), wherein X
1
represents a halogen atom, into a nucleophilic reagent, (Z)-4-undecenyl compound, of the following general formula (2), wherein M
1
represents Li or MgZ
1
, and Z
1
represents a halogen atom or a (4Z)-4-undecenyl group, subjecting the nucleophilic reagent, (Z)-4-undecenyl compound (2), to an addition reaction with propylene oxide of the following formula (3) to obtain (Z)-7-tetradecen-2-ol of the following formula (4) and oxidizing (Z)-7-tetradecen-2-ol (4) thus obtained to form (Z)-7-tetradecen-2-one (5).