A plane bending fatigue test was conducted on Ti–6Al–4V, and the crystal grains where the fatigue crack initiated were identified from the crystal orientation map obtained by using the EBSD method. In addition, the slip system, which generated the fatigue crack initiation, was identified by calculating the out-of-plane component of the Schmid factor ( SF) of each slip system. As a result, fatigue cracks were found to occur owing to basal slip. In this study, the out-of-plane component of the SF was mapped by considering the effect of the crystal grain size. The results clarified that the number of crystal grains where fatigue crack may initiate can be limited by using the out-of-plane component of the SF and the grain size.