An image forming apparatus includes a communication device, a RAM, a job managing unit, and an external temporary memory area managing unit. The communication device performs data communication with an external user terminal apparatus. The job managing unit allocates a memory area required to execute a requested job and executes the requested job. When it is determined that the memory area can't be allocated in the RAM owing to shortage of a free area in the RAM, the external temporary memory area managing unit (a) identifies a user who issued a job execution request on the basis of user authentication, (b) identifies a user terminal apparatus corresponding the identified user, and (c) uses a storage device of the identified user terminal apparatus as a part or all of a memory area required to execute the requested job on the basis of data communication performed by the communication device.