A transition metal complex obtained by contacting a bipyridine compound represented by the formula (1): wherein R1, R2 and R3 represent a C1-C10 alkyl group which may be substituted, etc., and R4 and R5 represent a hydrogen atom etc., with a compound of a transition metal belonging to Group 9, 10 or 11, and a process for producing a conjugated aromatic compound comprising reacting an aromatic compound (A) wherein one or two leaving groups are bonded to an aromatic ring with an aromatic compound (A) having the same structure as that of the above-mentioned aromatic compound (A) or an aromatic compound (B) being structurally different from the above-mentioned aromatic compound (A) and having one or two leaving groups bonded to an aromatic ring, in the presence of said transition metal complex.