PURPOSE: To accurately inject a liquid chemical using the injector even when an injection object exists in a narrow place or moves by giving the injector composition in which a needle tip and a liquid chemical storage container are separated, the interval between the needle tip and the container is made to communicate with a flexible tube, and the needle tip is linearly driven and displaced by a driving part using a shape memory alloy.

CONSTITUTION: When the temperature of either a gas or a liquid around a needle tip 1 is raised to a transformation temperature or higher, a coil spring 7 composed of the shape memory alloy is displaced from a plastic state (contraction) to an elastic state (expansion), and because of the expansion of the coil spring 7, the needle tip 1 is forcibly moved from a position in a figure in a left direction and thrusted into an injection object 8. After that, a movable part (piston) 9 of a liquid chemical storage container 3 is pressed and moved in the left direction in the figure using a certain means, because of this, a liquid chemical 10 is injected and sent in a flexible tube 2, and further, the liquid chemical 10 is injected from the tube 2 through the needle tip 1 into the injection object 8.