There is provided a manipulation instrument used in performing intradermal injection by means of a fluid injector that uses a multi-microneedle device, the instrument being simply configured to easily and reliably inject a desired amount of a fluid into a skin tissue, and being provided at low cost. The instrument (14) includes a selective movement mechanism (18) that moves the injector (12) between a first jutting position and a second position in a housing space (16c) of an outer cylinder (16), the first jutting position allowing needles (10c) of the device (10) to externally jut out from a one-end opening (16a) of the space by a first distance, the second position allowing the needles to externally jut out by a second distance shorter than the first distance. The fluid is discharged at the second position from the injector via the needles. The mechanism includes a rotational-linear movement conversion mechanism (20) interposed between the outer cylinder and the injector and moves the injector between the first and second positions along a longitudinal center line of the outer cylinder, in conformity with a direction and amount of rotation of the outer cylinder relative to the injector.