PROBLEM TO BE SOLVED: To provide a needleless syringe capable of administering a small amount of a drug solution contained in an ampule over a wide range. SOLUTION: A first spring 6 for returning a piston 4 that has moved forward from a first original position X1 in the direction of the other end 1b of the casing 1 in the direction of the first original position X1, and a forward movement of the piston 4. A revolver 81 that moves forward and backward following the movement and the backward movement, and a rotation drive mechanism 90 that rotates the revolver 81 by a constant angle are provided. The revolver 81 sequentially presses the end face of the plunger rod A2 of the ampoule A by the plurality of spiral stepped steps 87, and intermittently pushes the plunger rod A2 into the ampoule A. [Selection diagram] Fig. 1【課題】アンプルに収容した薬液を、少量ずつ広い範囲に投与することができる無針注射器を提供する。【解決手段】第１の原位置Ｘ１からケーシング１の他端部１ｂ方向へ往動させたピストン４を、第１の原位置Ｘ１方向へ復動させる第１のばね６と、ピストン４の往動及び復動に追従して往動及び復動するリボルバー８１と、リボルバー８１を一定角度ずつ回動させる回動駆動機構９０とを備える。リボルバー８１は、螺旋階段状の複数の段部８７によって、アンプルＡのプランジャーロッドＡ２の端面を順次押圧して、当該プランジャーロッドＡ２をアンプルＡ内に間欠的に押し込む。【選択図】図１
