An image forming apparatus has a storage portion, a mechanism control portion, and a main control portion. The storage portion stores information as to the apparatus. The mechanism control portion controls the operation of a mechanical system in the apparatus. The main control portion performs a job related to a function of the apparatus by controlling the operation of individual constituent elements of the apparatus, and on detecting an error that prevents continuation of the operation of the mechanical system included in the job being performed, feeds the mechanism control portion with an instruction to interrupt the control of the operation of the mechanical system, stores in the storage portion uncompleted data of the job corresponding to the operation of the mechanism control portion left uncompleted as a result of the interruption, reboots itself, and restarts the job by using the uncompleted data.