A monkey wrench includes a handle, a head, stationary jaw, a movable jaw and a jaw-moving element. The head is formed at an end of the handle and made with a side, a groove in the side and an opening in communication with the groove. The stationary jaw is formed on the head and made with a first nut-contacting face, a second nut-contacting face next to the first nut-contacting face, a bulge on the first nut-contacting face and a recess next to the bulge. The movable jaw is movably disposed in the groove and formed with a nut-contacting face and a bulge on the nut-contacting face thereof. The jaw-moving element is disposed in the opening and engaged with the movable jaw so that the jaw-moving element is operable to move the movable jaw relative to the stationary jaw.