The purposes of this paper is to demonstrate seismic performance evaluation procedure and seismic retrofit measures for an aseimic school building structure. The concept of deterioration is applied on the assessments of 1st seismic performance evaluation and performance reduction factor of in the 2nd seismic performance evaluation. The total assessments score of `1st evaluation was 0.84(grade D) which means the building needs to improve seismic performance by retrofitting. As a result of 2nd evaluation, columns are unsteady on the earthquakes with 200 year recurrence period, and it could not perform collapse prevention level with 1000 year recurrence period. Also, the effective response modification coefficient was quite less than criteria of KBC 2009. For retrofitting this building, damper was installed for improving system damping, and brace was set for enhancing strength and stiffness. Numerical results show that, all members was not destroyed and the effective response modification coefficient was larger than criteria of KBC 2009 as well.