1. An image processing method of decoding and displaying input encoded data, comprising: an input step of inputting fragmented encoded data which form image data; an upper limit value setting step of setting an upper limit value of a data size to be stored in a memory used to store the encoded data; a checking step of checking based on a data size stored in the memory, the upper limit value, and a data size of the encoded data input in said input step if the encoded data input in said input step can be stored in the memory; a region determination step of determining a region to be deleted in the image data; a delete step of deleting, when it is determined in said checking step that the encoded data input in said input step cannot be stored, data included in the region to be deleted, which is determined in said region determination step, for respective fragmented data, of data stored in the memory; and a control step of controlling, when it is determined in said checking step that the encoded data input in said input step can be stored, or after the data is deleted in said delete step, to store the encoded data input in said input step in the memory.