A method of administering a drug whereby a fine drug powder can be accurately administered to a target site (in particular, a target site in the body cavity) via fluidization and spraying with a gas by using a micro tube. Concerning the administration mode, in particular, the drug alone or a biopolymer is administered or the biopolymer is employed as a carrier in the above method. More specifically speaking, a method of administering a fine drug powder which comprises finely milling one or more types fine particles of the drug and/or the biopolymer, blending them each other, fluidizing the blend with a gas, then transporting the fluidized matter in a micro tube by the gas stream and spraying the fine drug powder from the tip of the micro tube toward the target site. Further, an administration method which comprises concentrically providing a capillary tube in the micro tube, supplying an aqueous solution of the drug and/or the biopolymer from the capillary tube into the gas stream and then mixing it with other fine particles of the drug and/or the biopolymer under transportation by the gas.