An administration instrument for medical use that can perform injection of a drug solution with stability and with great reliability. For example, at administration, it is possible to prevent a force that presses the injection button from acting in a direction of inserting the needle that is inserted into the skin deeper, and enables the administration under a stable state where the needle does not wobble, thereby alleviating physical and mental pain of the administration patient. With a structure in which an injection button is pressed at an angle that is not parallel to the needle with respect to a direction in which the needle is inserted into the skin, it is possible to prevent the force of pressing the injection button from being transmitted in a direction of inserting the needle into the skin deeper than the initial insertion of the needle, thereby achieving an administration under a stable state.