Olefin oligomerization catalyst and method for producing olefin oligomer in the presence of the same catalyst

A method for producing an olefin oligomer, comprising performing an olefin oligomerization reaction in the presence of an olefin oligomerization catalyst containing the following components (A) to (C):

• (A) a chromium compound,
• (B) an amine compound represented by the following general formula (1):
• (in the general formula (1), R1 to R4 may be the same or different from each other, and each represents a hydrogen atom, a halogen atom, a hydrocarbon group that does not contain a nitrogen-containing group or a phosphorus-containing group, a heterocyclic compound residue, an oxygen-containing group, a boron-containing group, an aluminum-containing group, a sulfur-containing group, a silicon-containing group, a germanium-containing group or a tin-containing group, and two or more thereof may be connected each other,
• Y represents a carbon atom having substituents R5 and R6 (a structure represented by —CR5R6—), R5 and R6 may be the same or different from each other, and each represents a hydrogen atom, a halogen atom, a hydrocarbon group, a heterocyclic compound residue, an oxygen-containing group, a nitrogen-containing group, a boron-containing group, an aluminum-containing group, a sulfur-containing group, a phosphorus-containing group, a silicon-containing group, a germanium-containing group or a tin-containing group, and R5 and R6 may be connected each other, and each of R5 and R6 may be connected to any one of R1 to R4,
• Z represents an integer of 1 to 10) and
• (C) at least one compound selected from the group consisting of
• (C-1) an organometal compound,
• (C-2) an organoaluminumoxy compound and
• (C-3) a compound reacting with a transition metal compound to form an ion pair.