A drug administration instrument (1) includes a syringe (11) and a sheath member (13). The syringe (11) has a tubular surrounding periphery (21), a discharge part (22) disposed at one end axially of the surrounding periphery 21, and a flange portion (24) disposed at the other end axially of the surrounding periphery (21) . The sheath member (13) is tubular, surrounding an outer circumference of an outer circumference of the surrounding periphery (21). The sheath member (13) also has a fitting part (15) that supports the surrounding periphery (21) and/or the discharge part (22).
