Part of an electrode, specifically a current collector and an active material layer, for a secondary battery is subjected to cutting processing to have a complex shape. For example, a stack of the first current collector and the first active material layer has a first slit and a second slit. The first slit extends from a first edge of the stack. The second slit extends from a second edge of the stack, is the slit closest to an electrode tab, and is not parallel or vertical to the longest edge of the current collector.