Secondary battery

An object of the present invention is to obtain a secondary battery that allows grasping a position of a mixture layer on an electrode and facilitates adjustment of positions of a positive electrode and a negative electrode. A secondary battery (100) of the present invention includes a negative electrode (32) that includes a strip-shaped copper foil (45) having both surfaces, negative electrode mixture layers (32a) on both the surfaces, a negative electrode foil exposed portion (32b), and insulating layers (31). The negative electrode foil exposed portion (32b) where the copper foil (45) is exposed is formed in an end portion on one side in a width direction of the copper foil (45). The insulating layers (31) are disposed on the negative electrode mixture layers (32a) and on the negative electrode foil exposed portion (32b). The insulating layer (31) includes a window portion (31a) at a position corresponding to a boundary part between the negative electrode mixture layer (32a) and the negative electrode foil exposed portion (32b). An end portion of the negative electrode mixture layer (32a) is visually recognizable from the window portion (31a).