An organic material removing device includes: a container for storing a composite material containing an inorganic material and an organic material decomposable by a treatment liquid; a treatment tank including an accommodation portion for accommodating the container, a treatment liquid inflow portion for allowing the treatment liquid to flow in, and a treatment liquid outflow portion for allowing the treatment liquid to flow out; temperature control means for heating or cooling the treatment liquid; and a treatment liquid circulation means for allowing the treatment liquid to flow in from the treatment liquid inflow portion into the treatment tank and allowing the treatment liquid in the treatment tank to flow out from the treatment liquid outflow portion.