An image forming apparatus (1) includes a fixing device (20; 20S) including a fixing rotary body (21) and a heater (23) for heating the fixing rotary body (21). An opposed body (22) contacts the fixing rotary body (21) with releasable pressure therebetween to form a fixing nip (N) therebetween through which a recording medium is conveyed. A heat shield (27; 27S) is interposed between the heater (23) and the fixing rotary body (21) and movable in a circumferential direction of the fixing rotary body (21) to shield the fixing rotary body (21) from the heater (23) in a variable circumferential direct heating span (±) of the fixing rotary body (21) where the heater (23) is disposed opposite the fixing rotary body (21) directly. A controller (90) halts the heat shield (27; 27S) instantly when a fault occurs during a print job.