Abstract: To enable high-added-value low-specific-gravity hollow particles to be efficiently mass-produced by using, as a raw material, coal ash discharged when coal is combusted; enriching low-specific-gravity hollow particles contained in the raw material coal ash by classification to reduce the weight of the coal ash to be subjected to wet specific gravity separation; subjecting the raw material coal ash which have been reduced in weight to wet specific gravity separation to obtain low-specific-gravity components; and dehydrating and drying the low-specific-gravity components.