Growing interest in robot colony has led to initial experimental applications in biology, sociology, and synecology. Especially, it is noticeable that some researchers have tried to study on robot colony using evolutionary computational. In this paper, we present an evolutionary robot colony model and analyze their behavior for leadership characteristics in group of robots. Each robot has its own social position: leader, follower, and stranger. Leaders have responsibility of the existence of its group while followers choose their behavior going after their leaders'. Strangers behave independently without a leader or a follower. Transition between social positions is controlled by simple rules and probability, and behaviors change adaptively to the environment using evolutionary computation. Simulation has been conducted with 2-D based robot simulator Enki of EPuck mobile robots. Through experiments, we have found that the more centralized structure emerges in the evolutionary robot colony with a few leaders and safety behavior policy when facing with a difficult condition.