Low-specific-gravity hollow particles having high added value can be efficiently mass-produced by using coal ash discharged from the coal firing step as the raw material, classifying the coal ash to collect low-specific-gravity hollow particles contained in the coal ash and to reduce the coal ash to be subjected to wet gravity separation, subjecting the reduced coal ash to wet gravity separation to recover a low-specific-gravity component, and dehydrating and drying the low-specific-gravity component.