A fuser device fusing a developer image on a medium includes a stable first unit, a movable second unit, and a movement mechanism moving the second unit between first and second positions. The first unit includes an endless first belt and a rotatably fuser member about a rotation shaft inside the first belt, the second unit includes an endless second belt, a pressure application member rotatably held about another rotation shaft displaceable inside the second belt, and a first bias member that biases the pressure application member toward the fuser member, and the pressure application member at the first position presses the fuser member such that a nip part is formed between the pressure application member and the fuser member, and at the second position, is detached from the fuser member so that the nip part is eliminated.