1. An image processing apparatus capable of executing at least one of a plurality of image processing jobs including a copy job, a FAX job, a print job, and a scan job, the image processing apparatus comprising: a first receiver operable to receive one or more of the plurality of image processing jobs; a second receiver operable to receive one or more maintenance jobs necessary for maintaining the image processing apparatus; a job register operable to register therein the received image processing jobs and the received maintenance jobs; and a controller operable to control execution of the registered image processing jobs and the registered maintenance jobs, with reference to the job register, wherein when the controller judges a next job registered in the job register is an image processing job, the controller prevents the execution of the judged next job when the judged next job requires prohibited functions corresponding to an executing maintenance job, wherein when the judged next job is a maintenance job, the controller stores prohibited functions corresponding to the judged next job and prevents the subsequent execution of jobs that require the prohibited functions, and wherein if a maintenance job and an image processing job that are executable in parallel with each other are registered in the job register, the controller executes the maintenance job and the image processing job in parallel with each other.