In an image processing method and apparatus for decoding and displaying input encoded data, the upper limit value of the data size to be stored in a memory that stores fragmented encoded data which form image data is set. It is checked based on the data size already stored in that memory, the upper limit value, and the data size of the input encoded data, if that input encoded data can be stored in the memory. If it is determined that the input encoded data cannot be stored in the memory, a region to be deleted in the image data of the data stored in the memory is determined. Data included in the determined region to be deleted is deleted for each fragmented data as a unit. If it is determined that the input encoded data can be stored in the memory, or after the data is deleted, the input encoded data is stored in the memory.