A switching device of a ratchet wrench includes two engaging members respectively mounted to two rods of an operation member. The operation member has a polygonal shank which extends through the board of the head of the wrench and is connected with a switch. The operation member swings by pivoting the switch so as to control the either of the two engaging members to be engaged with the ratchet driving member. The operation member has a positioning tube, and a bead and a spring are located in the positioning tube. The bead is engaged with one of two recesses of a cover fixed to the head of the wrench when the operation member is pivoted. The cover has a flange on which a locking member is pressed. The locking member is engaged with a fixing portion in the inner periphery of the space.