An image forming apparatus includes an image forming device, a transport belt, an optical sensor, an ultrasonic sensor, and a controller. The transport belt transports the recording sheet. The optical sensor emits light to the transport belt, and receives the light reflected by the transport belt. The ultrasonic sensor transmits ultrasonic wave to the transport belt, and receives the ultrasonic wave transmitted through the transport belt. The controller decides whether an output from each of the optical sensor and the ultrasonic sensor represents a normal value or an abnormal value, and executes predetermined control, depending on a combination of decision results about the respective outputs from the optical sensor and the ultrasonic sensor.