A printer in which, while achieving a stabilization of image quality by process control processing, the generation of unnecessary wait time to the user, shortening of lifespan of the apparatus and needless consumption of toner caused by unnecessary execution of the process control processing can be better suppressed than in the prior art. An NVRAM serving as non-volatile information storage device in which stored information is retained even if the supply of power from an engine unit power source circuit is cutoff is provided in an engine unit, and timing signal information output from a timing circuit when the process control processing is executed is stored in the NVRAM, the engine unit being configured so as to judge, when power supply from the engine unit power source circuit starts, whether or not process control processing is to be executed in accordance with the timing signal information stored in the NVRAM and the timing signal output from the timing circuit.