A hand tool having an adjustable head comprises a head, a handle, a fastening device and a joint lock mechanism, characterised in that: a bottom side of a concave pivotal portion of the handle has an inclining surface inclining forwardly from a first side of the concave pivotal portion to a second side of the concave pivotal portion; the joint lock mechanism comprises: a first engaging device and a second engaging device; the second engaging device comprises a pull button and a biasing device. The pull button is moveable from an unlocked position at the first side of the concave pivotal portion to a locked position at the second side of the concave pivotal portion. The biasing device is disposed at a front end such that when the pull button is at an unlocked position, a gap is formed between a rear end of the pull button and the bottom side of the concave pivotal portion; when the pull button is at a locked position, a front end of the pull button is adapted to engage the first engaging device.