This drug-filled synthetic resin ampule 1 is provided with an ampule body 2 and a drug 8 housed within the ampule body 2. The ampule body 2 is provided with a tip-side sealing part 3, a hollow part 21, and an annular breakable part 5 provided between the tip-side sealing part 3 and the hollow part 21. The tip-side sealing part 3 is provided with a flat plate part 32 for grasping formed at an upper part, and an internal top surface part 37 exposed within the hollow part 21. The breakable part is provided with an annular minimum-diameter part 51. The minimum-diameter part 51 is close to an annular peripheral edge part 37a of the internal top surface part and is located above the annular peripheral edge part 37a of the internal top surface part 37.
