A syringe holder configured to hold a syringe that comprises a body section having a cylindrical shape capable of being filled with a pharmaceutical liquid therein, a discharge portion formed at a distal end portion of the body section, a flange that is formed at a proximal end portion of the body section and includes a long diameter portion apart from a central axis of the body section by a predetermined distance and a short diameter portion apart from the central axis by a distance shorter than the predetermined distance of the long diameter portion, and a screwing portion that is provided to the discharge portion and is configured to screw an administration component to administer the pharmaceutical liquid to a biological body, the syringe holder comprises: a barrel body having a cylindrical shape, and being configured to cover at least an outer peripheral surface of the flange of the syringe; a holder opening provided to the barrel body, the holder opening being configured for inserting the syringe; a fixing claw configured to fix a surface of the flange in a side close to the holder opening; a fixing projection configured to fix a surface of the flange in a side opposite to the holder opening; a deformation promoting portion provided close to an end portion of the fixing claw in a side opposite to the holder opening (41 a), the deformation promoting portion being configured to promote the fixing claw to deform outward in a radial direction of the barrel body when the long diameter portion of the syringe inserted from the holder opening climbs over the fixing claw; a rotation restricting portion configured to come into contact with the short diameter portion so as to restrict the syringe from rotating in a circumferential direction with respect to the barrel body; and a radial movement-restricting portion provided close to the deformation promoting portion, the radial movement-restricting portion being configured to come into contact with the long diameter portion so as to restrict the syringe from moving in the radial direction with respect to the barrel body, wherein the deformation promoting portion is a through hole that penetrates a side wall of the barrel body, and the radial movement-restricting portion is a projection that is provided so as to close a part of the through hole, characterized in that the projection connects a distal end of the through hole and a proximal end thereof such that a distal end portion of the radial movement-restricting portion is formed thinner than a proximal end portion of the radial movement-restricting portion that is configured to come into contact with the long diameter portion, or the projection extends in a direction opposite to the holder opening from the end portion of the fixing claw in the side opposite to the holder opening and extends to part of the way in an axial direction of the through hole such that the projection has a free end portion in the side opposite to the holder opening. a barrel body having a cylindrical shape, and being configured to cover at least an outer peripheral surface of the flange of the syringe; a holder opening provided to the barrel body, the holder opening being configured for inserting the syringe; a fixing claw configured to fix a surface of the flange in a side close to the holder opening; a fixing projection configured to fix a surface of the flange in a side opposite to the holder opening; a deformation promoting portion provided close to an end portion of the fixing claw in a side opposite to the holder opening (41 a), the deformation promoting portion being configured to promote the fixing claw to deform outward in a radial direction of the barrel body when the long diameter portion of the syringe inserted from the holder opening climbs over the fixing claw; a rotation restricting portion configured to come into contact with the short diameter portion so as to restrict the syringe from rotating in a circumferential direction with respect to the barrel body; and a radial movement-restricting portion provided close to the deformation promoting portion, the radial movement-restricting portion being configured to come into contact with the long diameter portion so as to restrict the syringe from moving in the radial direction with respect to the barrel body, wherein the deformation promoting portion is a through hole that penetrates a side wall of the barrel body, and the radial movement-restricting portion is a projection that is provided so as to close a part of the through hole, characterized in that the projection connects a distal end of the through hole and a proximal end thereof such that a distal end portion of the radial movement-restricting portion is formed thinner than a proximal end portion of the radial movement-restricting portion that is configured to come into contact with the long diameter portion, or the projection extends in a direction opposite to the holder opening from the end portion of the fixing claw in the side opposite to the holder opening and extends to part of the way in an axial direction of the through hole such that the projection has a free end portion in the side opposite to the holder opening.