In this paper, the average cost calculation, which is not rely on discount rates, is investigated to evaluate the life cycle cost for the bridge components management. By assuming that the concerned bridge is under the perpetual usage, it is shown that the average cost evaluation becomes free from the conditionality for life-cycle cost evaluation : i.e., the setting of the target year of evaluation period as well as the current health-states of the bridge components. The expected cumulative life cycle cost defined for the arbitrary duration starting from the present time can be divided into the sum of the average annual cost and the relative cost conditionally defined upon the health states of the bridge components at the present time. It is also discussed that the average optimal maintenance strategies, which are evaluated by the evaluation scheme presented in the paper, can be obtained by the average cost minimizing Markov decision model. The validity of the model is investigated by a case study dealt with an actual highway bridge.