<p>This plastic ampule is obtained from a single plastic layer consisting only of cyclic polyolefin having a glass transition temperature of 50°C to 104°C and integrally comprises: an ampule body that is formed in a bottle shape with a top and a bottom and wherein a pouring opening for pouring out the drug solution is formed in the top; a cap fitted on said ampule body so as to seal said pouring opening; and a thin-walled part that is thinner than the ampule body and the cap, is formed in the circumferential direction of the pouring opening, and connects the ampule body with the cap. The ampule is opened by breaking or twisting between the ampule body and the cap with the thin-walled part as the point of cleavage.</p>
