Scalable self-reconfiguration of an M-TRAN modular robotic system is presented herein. Possible configurations are restricted to those of a symmetric planar type, which are made by an arbitrary number of M-TRAN modules. A logical model of such configurations is made in which each module is represented as a square cell, where self-reconfiguration is represented by cooperative motions of two neighbor cells. Based on the concept, programs for simulations and experiments were developed. Experiments of simple self-reconfigurations using local communication between modules by infrared light were successful.