The objective of the present invention is to provide a capsule filling composition which can stably produce a capsule formulation by suppressing the flow of components out of the capsule body during capsule filling, regardless of the compressibility of an active ingredient such as drugs and health foods, so that a favorable capsule filling can be achieved; and a method of producing a capsule formulation with the use of such a capsule filling composition, as well as a capsule formulation. The objective is achieved by a method of producing a capsule formulation, comprising subjecting a capsule filling composition containing an active ingredient and a cellulose ether powder to a funnel system powder filling or a die-compression system powder filling to obtain the capsule formulation, and the like.