To change behavior, and maintain growth by replaceably arranging replacing modules in a machine body, and rewriting a behavior library in the machine body by a behavior library of the replacing modules when replacing the replacing modules.

Plural kinds of replacing modules are prepared for a head part module 3 and a leg part module 4 to be optionally replaced by a desired of a user. A basic program for moving the respective modules 3, 4 is stored in memories 3b, 4b of the respective modules 3, 4. When replacing the respective modules 3, 4, new device data 5 stored in the memories 3b, 4b is sent to a rewriting processing part 2f of a robot body 2 to rewrite an existing feeling model and a behavior library by the rewriting processing part 2f, thereby performs another behavior when replacing the modules 3, 4 as well as to maintain learning in a previously used module.