A stapler includes a main body, a striking plate, a trigger plate, an elastic plate, a top cover, a restoring spring, a base, and a safety device. Thus, the positioning portions of the elastic plate have the same size and the same bent angle to provide a force which is distributed on the striking plate evenly to drive the striking plate to perform the stapling action exactly and smoothly, thereby enhancing the stapling efficiency of the stapler. In addition, when the base is detached from the main body, the top cover is locked by the positioning block to prevent the top cover from being pressed unintentionally so that the striking plate will not be triggered by pressing the top cover so as to protect the user's safety.