A ratchet wrench includes a handle with an enlarged head formed on one end of the handle and a neck integrally formed between the handle and the enlarged head. A cavity is defined in and extends through the enlarged head. The cavity has an axis perpendicularly corresponding to that of the handle. A ratchet set is pivotally received in the cavity and has multiple rotors rotatably abutting an inner periphery of the cavity. An actuated stub centrally extends from the ratchet set for driving a workpiece. A channel is defined in the neck, thereby a thickness between the channel and the cavity is equal to the thickness between the inner periphery of the cavity and an outer periphery of the enlarged head to promote the effect of heat treatment in the inner periphery of the cavity.