Secondary battery

A cap plate (100) for sealing a case (180) housing an electrode assembly (150) includes a cover portion (100a) that covers the electrode assembly (150), a support portion (100b) having a first thickness (T S ), the support portion (100b) being offset along a first direction from the cover portion (100a), and a reinforcing portion (100c) that connects the cover portion (100a) and the support portion (100b). The reinforcing portion (100c) has a processing thickness (T r ) that is greater than the first thickness (T S ), the first thickness (T S ) and the processing thickness (T r ) being measured along the first direction.