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 (54) is: the injector (52) in the housing space (56c) of the outer cylinder (56), and the needle (50c) of the body (50b) of the device is retracted into one end opening of the space. A mechanism (58) for sequentially moving between an initial position, a first position protruding outward from the opening to a first distance, and a second position protruding outward to a second distance shorter than the first distance； Fluid flows out from the injector through the needle at two positions, and the mechanism is a unit (58a) for biasing the injector to an initial position by magnetic force between the outer cylinder and the injector, First and second stoppers (58b, 58c) capable of appearing and retracting on the outer peripheral wall, and engaging portions (58d) for selectively engaging with these stoppers on the outer peripheral wall of the injector and selectively disposing the injector at the three positions. And comprising.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（５４）は：外筒（５６）の収容空間（５６ｃ）中で上記注入器（５２）を、上記デバイスの本体（５０ｂ）のニードル（５０ｃ）が上記空間の一端開口内に引っ込められた初期位置、上記開口から第１距離まで外部突出された第１位置、第１距離より短い第２距離まで外部突出された第２位置、間で順次移動させる機構（５８）；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で磁力により上記注入器を初期位置に付勢するユニット（５８ａ）、外筒の外周壁に出没可能な第１及び第２ストッパ（５８ｂ，５８ｃ）、上記注入器の外周壁でこれらストッパと選択係合し上記注入器を上記３つの位置に選択配置する係合部（５８ｄ）と、を備える。
