A drug-filled synthetic resin ampule has an ampule body capable of standing by itself and a drug accommodated inside the ampule body. The ampule body has a tip part positioned at an upper part thereof when the ampule body stands by itself, a hollow part having a drug accommodation portion, and a breakable part provided between a lower portion of the tip part and an upper portion of the hollow part. The tip part has pressing portions, for guiding a pressing force applied thereto respectively in a predetermined direction when an operation of breaking the breakable part is performed. The hollow part has a bottom surface part for allowing the ampule body to stand by itself. The bottom surface part has extension portions extended in predetermined directions (X-direction, Y-direction) in which the pressing force applied to the pressing portions respectively is guided when the operation of pressing the pressing portion is performed to break the breakable part.