A triarylamine dimer derivative is represented by the following chemical formula [1] (in the chemical formula [1]: —Ar1, —Ar2, —Ar3 and —Ar4 are aryl groups being to have a substitutional group respectively, —R1 and —R2 are same or different to each other and one thereof is selected from the group consisting of a hydrogen atom, an alkyl group, an alkoxyl group and a halogen atom; m and n are from 0 to 4; and with a proviso that —Ar1 and —Ar2, —Ar3 and —Ar4 are being to bind respectively to compose a cyclic structure group having a nitrogen atom) having an amorphous phase indicated by spectrum of powder X-ray diffractometry. The triarylamine dimer derivative is used for a charge transport material, an electrophotographic photosensitive conductor having thereof, an electroluminescence elemental device having a hole transport material thereof.