PURPOSE: To provide a method, for producing α-olefin by oligomerization of ethylene, capable of suppressing production of a polymer and capable of selectively and efficiently providing a 4-14C α-olefin in an oligomer.

CONSTITUTION: Ethylene is oligomerized in the presence of (A) a zirconium compound of formula I [R1 and R2 each is methyl or a halogenated methyl whose at least one H is replaced with a halogen, with the proviso that R1 and R2 are not simultaneously methyl; X1 is a 1-8C alkoxyl a 2-4C fluorinated alkoxyl in which all hydrogen atoms at least β-position are replaced with F or a halogen; (n) is 1-4] and (B) an organoaluminum compound of formula II [R3 is a 1-20C alkyl; X2 is a halogen; (m) is 1, 1.5, 2 or 3], preferably under 10-100-kg/cm3 ethylene pressure and at 20-100°C to produce the objective α-olefin. The component A is preferably used in an amount of 0.001-10mm mol, especially 0.01-1mm mol based on 1-mol ethylene and the component B is preferably used in an amount of 1-200mol, especially 20-100mol based on 1mol of the component A.