Active magnetic bearing (AMB) is an ideal bearing solution for high performance and energy efficient applications. Proper operation of AMB can be achieved only with advanced feedback control techniques. An identified system model is required for synthesizing high performance model based controllers. System identification is the preferred method for obtaining an accurate model. Therefore, it becomes a prerequisite for the commissioning of AMB. System identification for commissioning poses some challenges and special requirements. In this thesis, system identification of AMB is approached within the context of commissioning. A procedure for identification is developed and applied to experimental data from a prototype AMB system. The identification procedure is based on the so called prediction error method, and it has been performed in the frequency domain. A linear state-space model, along with the required parameters, is successfully identified.