An adjustable ratchet wrench includes a wrench body, a ratchet, a positioning member, and a movable device. A fixed clamp portion is disposed on the inner periphery of the ratchet. The positioning member is disposed on the inner periphery of the ratchet. The movable device is disposed on the inner periphery of the ratchet and movably connected with the positioning member. The movable device has a movable clamp portion, which forms a tool receiving hole with the fixed clamp portion for receiving a workpiece. By used of the movable device, the size of the tool receiving hole is adjusted for being applicable to workpieces with different sizes, facilitating the utility of the present invention.