In order to secure the reliable electric power supply, it is necessary to undertake new extension, renewal and maintenance works of various power system apparatuses. These works generally deteriorate power supply reliability in system operations compared with normal operations without outage works. The most important thing is that outage works are appropriately executed with system configurations to avoid reducing supply reliability as much as possible. The author has so far proposed that it formulizes an outage work planning as a combinatorial optimization problem of the power system configuration, considering the minimization of power supply shortage over the whole period. The proposed system generates a huge number of candidates for working configurations satisfying various operational constraints in the process for solving the problem. This paper presents a method for making outage work planning with these candidates by using Particle Swarm Optimization (PSO) which is a kind of evolutional computation methods. We also carried out numerical simulations to confirm the effectiveness of the proposed method.