To solve an environmental problem wherein the offensive smell of compost and excretions can not be removed even if they are dried in a case that conventional compost and the excretions of livestock are treated to be converted to fertilizer or fuel.

A deodorizing solution is injected in the compost and the excretions of the livestock to be together stirred along with the compost and the excretions and the resulting stirred solution is subjected to solid-liquid separation when the BOD value thereof becomes a predetermined value or below to be separated into a solid substance and a liquid component. The solid substance is finely divided and dried to be preserved in a state that an offensive smell is removed, and the liquid component is reutilized as the deodorizing solution after the SS value thereof becomes a predetermined value or below.