We have surveyed the affected area of western Japan heavy rain in 2018, with purposed to clarify evacuation behavior of vulnerable people and estimation of blast pressure from an aluminum factory explosion as a complex disaster. We conducted interview surveys targeted all vulnerable people in Shimobara District, Okayama Prefecture and 18 people from 16 households responded, and they finally evacuated without any casualties. For evacuation decision factors, "Explosion of aluminum factory", "Visits by relatives", "Visits by community disaster prevention organization" were the most frequent.