Abstract: Provided is a dosage adjuster for a syringe including: a dosage setting part configured to set the amount of dosage usable out of a liquid medicine filled in the syringe; and a setting restriction part configured to switch between a restricted state in which change in setting of the amount of dosage set by the dosage setting part is restricted and a permissible state in which the change in the setting of the amount of dosage by the dosage setting part is permissible.

Abstract: An object of the present invention is to provide a syringe auxiliary tool capable of enhancing the safety during piercing an injection needle. The syringe auxiliary tool includes a housing that houses the syringe and has a contact surface that comes into contact with a living body, a moving part that is slidably attached to the housing in order to switch between an advanced position at which the injection needle of the syringe is located forward of the contact surface and a retracted position at which the injection needle is retracted rearward of the contact surface, a biasing means that biases the moving part rearward, and an operation member that slides the moving part forward.