Motion data of a model object is blended based on individual blend ratios A and B that are set for each bone of a skeleton. The individual blend ratios B for bones at end portions of the skeleton (weapons, hands, and feet) are high whereas those for main structural components (pelvis and chest) are low. A general blend ratio that is set uniformly for all the bones of the skeleton is also used. A plurality of motion control sections are made to operate simultaneously in parallel to select the motion data, based on motion scripts in which motion data to be selected and motion script switching conditions are defined, and the selected motion data is blended. A group of transitional motion scripts and a group of attack motion scripts are allocated to the first and second motion control sections, and transitional motions and attack motions are blended.