A fixing device includes a pressure mechanism and a pressure adjustment mechanism. The pressure mechanism includes a pressing member holding one of the pressure member and the heating member and a biasing member biasing the pressing member in a direction toward or away from the other of the pressure member and the heating member. The pressure adjustment mechanism includes an eccentric cam. The pressure adjustment mechanism uses one of small-diameter and large-diameter parts formed in the outer peripheral surface of the eccentric cam to allow the pressure mechanism to give the nip pressure, and uses the other of them to allow the pressure mechanism to release the nip pressure. When the large-diameter part is used to allow the pressure mechanism to give or release the nip pressure, the eccentric cam constantly receives reaction force urging it to rotate in a direction toward the small-diameter part.