The present invention discloses a vesicle which is excellent in structure stability and environmental responsiveness and also can be produced by a simple operation. More particularly, the present invention discloses a vesicle comprising a membrane formed of a first block copolymer containing a non-chargeable hydrophilic segment and a chargeable segment, and a second block copolymer containing a non-chargeable hydrophilic segment and a chargeable segment having an electric charge which is opposite to that of the chargeable segment of the first block copolymer.
