A lock mechanism includes a driving arm having an arm portion and a fixing portion and a lock rod having first and second ends and a pivot portion. The pivot portion is pivoted to one of a cover and a casing. The fixing portion is disposed on the one of the cover and the casing so as to make a free end of the arm portion interfere with an interference portion of the lock rod. The arm portion swings to a first position or a second position when receiving force. When the first end or the second end is pressed, the interference portion drives the free end to make the arm portion swing to the first or second position, so as to make the lock rod move to a locking position for fixing the cover on the casing or a releasing position for releasing the cover from the casing.