Background: Ultrasonication effectively breaks supersaturation and forces amyloid fibrillation. Results: A high-throughput analysis of amyloid fibrillation showed that, although the lag time varied depending on the conditions, its coefficient of variation was constant. Conclusion: The large fluctuation in the lag time originates from a process associated with a common amyloidogenic intermediate. Significance: High-throughput analysis is powerful enough to clarify the mechanisms of supersaturation-limited phase transitions of proteins.