A fixing device includes a first rotatory body, a heater, a pressure receiving member, a supporting member, a second rotatory body, a position detection section, and a determination section. The position detection section detects a position of an outer circumferential surface of the first rotatory body in terms of a radial direction. The determination section determines a rotation state of the first rotatory body based on a result of detection by the position detection section. The position detection section includes a first position detection member and a second position detection member. The first position detection member is located upstream of a fixing nip in terms of a rotation direction of the first rotatory body. The second position detection member is located downstream of the fixing nip in terms of the rotation direction.