An electrochemical device includes an electrode assembly, a packaging bag accommodating the electrode assembly, and electrode terminals connected to the electrode assembly. The packaging bag includes a first seal edge, a third seal edge, a first sidewall connected to the first seal edge, a second sidewall connected to the third seal edge, and a third sidewall. The first sidewall includes a first section connected to the second sidewall; and an arc-shaped second section connected to the third sidewall and the first section. The first seal edge includes a first hem connected to the first section and a second hem connected to the first hem. The first hem is disposed along the thickness direction of the electrode assembly. The second hem includes a first part and a second part. The second part is connected to the second section and the first part and abuts against the second section.