When intradermal injection is performed with a fluid injector using a multi-microneedle device, an inexpensive operation tool is provided with a simple configuration that can easily and reliably inject a desired amount of fluid into skin tissue. The instrument (14) is: the syringe (12) in the housing space (16c) of the outer cylinder (16), and the needle (10c) of the device (10) is first from the one end opening (16a) of the space. A selective movement mechanism (18) for moving between a first protruding position protruding outward to a distance and a second position protruding externally to a second distance shorter than the first distance, wherein the injection is performed at the second position. The fluid flows out of the container through the needle, and the mechanism is interposed between the outer cylinder and the injector, and the length of the outer cylinder corresponds to the direction and amount of rotation of the outer cylinder relative to the injector. A rotation-to-straight movement conversion mechanism (20) for moving the injector between the first position and the second position along a direction center line；マルチマイクロニードルデバイス使用流体注入器で皮内注射する場合、容易に確実に短時間で所望量の流体を皮膚組織に注入出来る簡易な構成で安価な操作器具を提供する。 上記器具（１４）は：外筒（１６）の収容空間（１６ｃ）中で上記注入器（１２）を、上記デバイス（１０）のニードル（１０ｃ）が上記空間の一端開口（１６ａ）から第１距離まで外部突出させた第１突出位置、第１距離よりも短い第２距離まで外部突出された第２位置、の間で移動させる選択移動機構（１８）；を備え、第２位置で上記注入器から上記ニードルを介し流体が流出され、上記機構は、外筒と上記注入器との間に介在され、上記注入器に対する外筒の相対的な回転の方向及び量に対応し外筒の長手方向中心線に沿い上記注入器を前記第１位置と前記第２位置との間で移動させる回転－直進移動変換機構（２０）を含む。
