Provided is a secondary battery, including: an electrode assembly, a packing bag, an electrode lead and an insulation part; the electrode assembly is housed in the packing bag having a sealing part on edge, and the electrode lead is connected to the electrode assembly and passes through the sealing part. The sealing part includes a main body area, a first step area and a first transition area which are located on same side of the electrode lead along width direction, and the main body area, first transition area and first step area are successively arranged along direction approaching the electrode lead; the insulation part is wrapped around the electrode lead, and has a first portion which is located on a side of the electrode lead close to the main body area along width direction and covered by the first step area on both sides in thickness direction.