To provide safe and preferable opening operation of an ampule container made of synthetic resin formed by two axis stretch blow molding while maintaining good moldability at its head side without losing easiness for detaching at its fragile part.

A wall thickness a of a fragile part 7 molded by caving a peripheral groove which is V shape on an outer peripheral face and provided all around the outer peripheral face is set to as a small value as possible in a range that maintains good moldability. On an inner peripheral face part 8 positioned near side of the fragile part 7, a step part 9 is provided all around the inner peripheral face part. A stress concentration part when detaching processing of a head part 6 is formed on the inner peripheral face side by the step part 9, so as to detach the head part 6 stably.