A combination lock includes: a base mounted securely on a suitcase; a case locking mechanism mounted on the base and operable to move between locking and releasing positions; a dial lock mounted on the case locking mechanism, including a lock controlling member, and operable between locking and releasing states through operation of the lock controlling member; and a key-operated unlocking unit mounted on the case locking mechanism, including a core, and operable in a manner that the case locking mechanism is permitted to move from the locking position to the releasing position when the core is moved from a first angular position to a second angular position.