A hand tool having an adjustable head with a joint lock mechanism. The joint lock mechanism comprises a first engaging device, a push button, a second engaging device, a first elastic device and a second elastic device. The push button is formed with a through hole and a first engaging portion. The second engaging device passes through the through hole and is disposed with a second engaging portion. When the first engaging portion engages the second engaging portion, the front end of the first engaging portion abuts the front end of the second engaging portion such that the second engaging device engages the first engaging device and is prevented from moving.