Disclosed is an injection gadget corresponding to an end-effector such as a rescue robot or the like. The injection gadget is configured such that an injection needle is disposed inside an injection assembly, an injection liquid is provided between a cylinder and a piston of the injection assembly, and the piston is moved by an elastic force of a spring previously compressed inside the cylinder so that the injection needle protrudes to the outside of the injection assembly and the injection liquid is ejected, and includes a bracket that replaceably mounts the injection assembly, a main body that is connected to the bracket and includes a first body space portion of which one side surface facing the bracket and the other side surface are open to pass through each other and a second body space portion that is disposed next to the first body space portion, a controller that is mounted in the second body space portion, a linear actuator that moves a transfer shaft in accordance with a control signal of the controller, and a pusher that is disposed between the linear actuator and the injection assembly, and transmits a force of the linear actuator toward the injection assembly so that a locking pin of the bracket is deviated from locking guides of the piston of the injection assembly.