The present invention intends to provide a simple process for preparing a triarylamine dimer without using any expensive chemicals, the process being able to achieve high reaction yield and being advantageous to be carried out on an industrial scale. The present invention provides a process for preparing a triarylamine dimer (I) using the Ullmann reaction represented by the scheme:
wherein X represents a halogen atom, R 1 and R 2 represent independently a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom, Ar represents a phenylene group, or a naphthylene group, characterized in that the reaction accelerator is polyethylene glycol or di- or monoalkyl ether of polyethylene glycol.