A process for preparing a terminal conjugated alkadienal compound of the following general formula: CH 2 =CHCH=CH(CH 2) a CHO wherein "a" represents an integer of 1 to 15, the process comprising: dealkoxymethylating a dialkoxyalkenyl alkoxymethyl ether compound of the following general formula: R 1 CH 2 OCH 2 OCH 2 CH 2 CH = CH(CH 2) a CH(OR 2)(OR 3) wherein R 1 represents a hydrogen atom, an n-alkyl group having 1 to 9 carbon atoms, or a phenyl group, R 2 and R 3 represent, independently of each other, a monovalent hydrocarbon group having 1 to 15 carbon atoms, or R 2 and R 3 may form together a divalent hydrocarbon group, R 2 -R 3, having 2 to 10 carbon atoms, and "a" is as defined above, to prepare a dialkoxy-3-alken-1-ol compound of the following general formula: HOCH 2 CH 2 CH=CH(CH 2) a CH(OR 4)(OR 5) wherein R 4 and R 5 represent, independently of each other, a monovalent hydrocarbon group having 1 to 15 carbon atoms, or R 4 and R 5 may form together a divalent hydrocarbon group, R 4 -R 5, having 2 to 10 carbon atoms, and "a" is as defined above; halogenating the dialkoxy-3-alken-1-ol compound to prepare a 1-halodialkoxy-3-alkene compound of the following general formula: XCH 2 CH 2 CH=CH(CH 2) a CH(OR 4)(OR 5) wherein X represents a halogen atom, and R 4, R 5 and "a" are as defined above; subjecting the 1-halodialkoxy-3-alkene compound to an elimination reaction in the presence of a base to prepare a dialkoxy-1,3-alkadiene compound of the following general formula: CH 2 =CHCH=CH(CH 2) a CH(OR 4)(OR 5) wherein R 4, R 5 and "a" are as defined above; and hydrolyzing the dialkoxy-1,3-alkadiene compound to obtain the terminal conjugated alkadienal compound. wherein "a" represents an integer of 1 to 15, the process comprising: dealkoxymethylating a dialkoxyalkenyl alkoxymethyl ether compound of the following general formula: R 1 CH 2 OCH 2 OCH 2 CH 2 CH = CH(CH 2) a CH(OR 2)(OR 3) wherein R 1 represents a hydrogen atom, an n-alkyl group having 1 to 9 carbon atoms, or a phenyl group, R 2 and R 3 represent, independently of each other, a monovalent hydrocarbon group having 1 to 15 carbon atoms, or R 2 and R 3 may form together a divalent hydrocarbon group, R 2 -R 3, having 2 to 10 carbon atoms, and "a" is as defined above, to prepare a dialkoxy-3-alken-1-ol compound of the following general formula: HOCH 2 CH 2 CH=CH(CH 2) a CH(OR 4)(OR 5) wherein R 4 and R 5 represent, independently of each other, a monovalent hydrocarbon group having 1 to 15 carbon atoms, or R 4 and R 5 may form together a divalent hydrocarbon group, R 4 -R 5, having 2 to 10 carbon atoms, and "a" is as defined above; halogenating the dialkoxy-3-alken-1-ol compound to prepare a 1-halodialkoxy-3-alkene compound of the following general formula: XCH 2 CH 2 CH=CH(CH 2) a CH(OR 4)(OR 5) wherein X represents a halogen atom, and R 4, R 5 and "a" are as defined above; subjecting the 1-halodialkoxy-3-alkene compound to an elimination reaction in the presence of a base to prepare a dialkoxy-1,3-alkadiene compound of the following general formula: CH 2 =CHCH=CH(CH 2) a CH(OR 4)(OR 5) wherein R 4, R 5 and "a" are as defined above; and hydrolyzing the dialkoxy-1,3-alkadiene compound to obtain the terminal conjugated alkadienal compound.