In restructured power systems, the traditional approaches of unit maintenance scheduling (UMS) need toundergo major changes in order to be compatible with new competitive structures. Performing the maintenance on generating units may decrease the security level of transmission network and result in electricity shortage in power system; as a result, it can impose a kind of cost on transmission network as called security cost. Moreover, taking off line a generating unit for performing maintenance can change power flow in some transmission lines, and may lead to network congestion. In this study, generating unit maintenance is scheduled considering security and con-gestion cost with N-1 examination for transmission lines random failures. The proposed UMS approach would lead to optimum operation of power system in terms of economyand security. To achieve this goal, the optimal power flow(OPF) compatible with market mechanism is implemented.Moreover, the electricity price discovery mechanism aslocational marginal pricing (LMP) is restated to analyze the impacts of UMS on nodal electricity price. Considering security and congestion cost simultaneously, this novel approach can reveal some new costs which are imposed to transmission network on behalf of generation units; as aresult, it provides a great opportunity to perform maintenance in a fair environment for both generating companies(GenCo) and transmission companies (TransCo). At the end, simulation results on nine-bus test power system demonstrate that by using this method, the proposed UMS can guarantee fairness among market participants including GenCos and TransCo and ensure power system security.