A positioning device for a ratchet wrench contains: a driving head connecting with an operating handle and including an accommodating cavity, a toothed groove, and a slot, a depth of which is equal to the accommodating cavity. The driving head also includes an orifice and a horizontal notch, a depth of the horizontal notch is equal to the slot. The positioning device contains a rotatory block fixed in the driving head and including a first toothed section and a second toothed section; an abutting member fixed in the slot and including an elastic steel ball, plural locking teeth, an aperture, and a resilient element; a pushing post fixed in the horizontal notch of the driving head and including a peripheral recess, wherein one end of the pushing post is screwed with a screwing element; a cover locked on the driving head to cover the abutting member and the pushing post.