1. An image compression method for compressing a still image and a motion image to the same digital data format via an image processing apparatus, wherein the image processing apparatus includes an image analysis section, a control section, a motion image encoding section, and a recording medium section; wherein the image analysis section divides the still image into image segments and analyzes each image segment to compute image information, and determines the importance of each image segment and the relativity of each image segment with another image segment; wherein the control section determines an image segment encoding sequence in accordance with the importance and a picture type of each image segment in a way that the image having the low relativity to any other images in accordance with the relativity is assigned to a picture type having no reference relation in accordance with a motion image encode specification; and wherein the motion image encoding section performs a motion image encoding process on each image segment in accordance with the encoding sequence and picture type determined by the control section, makes the encode data of the same digital data format as a motion image, and records the encode data to the recording medium section.