An injector includes a support tube having one end surface to be brought into contact with skin, a movable tube advanceable in the support tube in the direction of the skin, an injection needle communicating with the movable tube, a plunger advanceable in the movable tube in the direction of the skin to introduce medicinal liquid filled in the movable tube to the injection needle, and a sealing material provided at the tip of the support tube and penetratable by the injection needle to penetrate the sealing material. In an initial state, the tip of the injection needle is sealed by the sealing material.