An image processing apparatus has a large number of image processing functions, in which resources necessary for code processing units can be suppressed while a large-scale decline in performance is prevented. The apparatus includes code processing units for executing coding and decoding of image data, and request-source task units (print function, scanner function and FAX transceive function), which request any one of the code converters to perform code conversion of image data. The number of request-source task units is greater than the number of code converters and a degree of priority has been set for each one. A determination unit always assigns the code converting units to processing requests from request-source task units having a high priority and, if there is an idle code converting unit, assigns the code converting unit to a processing request from a request-source task unit having a low priority.