An electrochemical device includes a housing including a body portion and a first portion, an electrode assembly, and a tab. In a second direction, the body portion includes a first wall and a second wall disposed opposite to each other. In a third direction, the body portion includes a first sidewall and a second sidewall disposed opposite to each other. The first portion includes a first seal edge and a second seal edge. The first seal edge is connected to the first sidewall and the second wall. The second seal edge is connected to the first seal edge. The second seal edge is disposed between the first seal edge and the first sidewall. The housing includes a first housing part and a second housing part disposed opposite to each other. The first housing part includes a first polymer layer. The second housing part includes a second polymer layer.