In this study, we examined the fatigue crack nucleation and propagation mechanisms of an AlSi sputtered thin film subjected to the quasistatic tensile test and cyclic loading test by scanning electron microscopy. An AlSi thin film with 1.0 wt% Si was prepared by dc magnetron sputtering at a substrate temperature of 260 ℃, followed by annealing at 490 ℃. Two types of uniaxial tensile test equipment were prepared, namely, manual tensile loading equipment and automatic tensile loading equipment. The combination of the use of manual-type equipment and electron backscattered diffraction analysis enabled us to visualize crystal grain subdivision mechanisms. The automatic-type equipment enabled us to understand fatigue crack propagation mechanisms in the AlSi thin film after crack nucleation originating from grain subdivision. A fatigue crack propagated in a zigzag manner under the low stress amplitude condition during the fatigue test, whereas it propagated straightly under the high stress amplitude condition. This phenomenon is discussed from the viewpoints of crack detouring around Si segregates and Si brittleness.