In this paper, for an ego-motion estimating problem of mobile robot, we propose a plug and play ego-motion estimator that a user can freely select the sensor type and flexibly install the sensor. In this algorithm, each sensor is dealt with a sensor unit that has some computing equipment, and each sensor unit estimates the ego-motion and the sensor parameter. Moreover, the sensor units are connected via a network, and the ego-motion estimate of each unit are exchanged each other. Then the exchanged information is fused by Covariance Intersection method, which is one of a decentralized estimator. By this, this algorithm can estimate ego-motion not affected by number of sensors and sensor type. Furthermore, user can flexibly install the sensors by this algorithm because sensor parameters are estimated in each unit and compensated information are exchanged each other. In addition to this high flexibility, an experimental results denotes that our method estimate ego-motion with adequate accuracy.