A wrench includes a handle, a head having a pivotal portion pivotably connected to an end of the handle, and a retaining mechanism for allowing the head to be pivotally moved to a desired position relative to the handle and retaining the head in the desired position. The pivotal portion of the head includes a fore part and a rear part with reference to a ratcheting direction of the handle. The fore part includes an arcuate outer surface section. The rear part includes a toothed section having a plurality of teeth. The toothed section has a dedendum circle located inside an area delimited by the arcuate outer surface section. Thus, the thickness of the fore part is not reduced, preventing damage to the torque-bearing section in the fore part during operation.