The power relay can easily control high voltage and high current through metallic contacts. In addition, it has the advantage in reasonable price. So it has been used in many applications. But the power relay has a weak point by mechanical movements. These mechanical movements cause the bouncing phenomenon. Arc and bouncing phenomenon are the main causes of electric abrasion and material erosion. In this study, mechanical repetitive experiments and repetitive experiments in electrically connected state are conducted. Then these two experimental results in terms of bouncing phenomenon and changes in the contact surface are compared. In all number of repetitions, contacts in an electrically connected state cause smaller number of bounce. Also, It has lower contents of silver on eroded surface than the other. The experimental results would be helpful to the further study of contacts life span.