We have investigated the pretilt angle of liquid crystals generated by photoalignment layers of polyimide containing azobenzene in the backbone structure (Azo-PI). Three different photoalignment layers were prepared by performing or not performing alkylamine vapor treatment on the precursor (polyamic acid: Azo-PAA) films. Octadecyamine (ODA) and N,N-dimethylhexadecylamine (DMHDA) were used as a primary and a tertiary alkylamines, respectively. When unpolarized light irradiation of 114 J/cm2 was performed at an angle of incidence of 45°, the pretilt angles generated by the conventional (without alkylamine vapor treatment), ODA-treated, and DMHDA-treated photoalignment layers were 1.4°, 19°, and 4.3°, respectively. From these results, we found that the pretilt angle generated by Azo-PI photoalignment layers increased by performing alkylamine vapor treatment but the degree of increase strongly depended on the class of alkylamine. To understand the increase in the pretilt angle by the alkylamine vapor treatments, the alignment behaviour of the Azo-PAA (PI) backbone structure in each preparation step was examined and discussed.