This paper describes the method of searching mobiles. There are various mobile around the robot, that is, pedestrians, bicycles, cars and so on. When the robot runs autonomy, the correspondence for a mobile is a problem. It is easy to avoid a stationary object, but it is difficult to avoid a moving object. This method searches a mobile around the robot using two laser range scanners, calculates the relative velocity vector of the mobile and sets the risk level considering the risk of collision with the robot from the vector in the mobile.