This study discusses the merits and challenges of using satellite data by investigating how well the number of disaster victims estimated from satellite images matches the actual number of evacuees in the case of the flood disaster caused by Typhoon Ulysses, which hit the Philippines in November 2020. In this case, the Sentinel-2 satellite captured optical images covering most of the two target basins in the following morning after the typhoon had left the islands, making it possible to confirm the inundation status for 80% of the basins’ municipalities. We analyzed the data to compare the number of victims estimated from the satellite images and the actual number of evacuees and revealed a large discrepancy between them. We investigate how well satellite images predict the presence or absence of potential victims and found that both optical and SAR images have a possibility to provide reliable inundation status to determine whether there are potential victims.