This paper describes the mechanical design of a microhead actuator for disk storage systems and its positioning control method. A new concept called “quasi collocation” is introduced to discuss the stability of positioning control systems for the structure. A simple actuator model is fabricated, and its dynamic characteristics are numerically and experimentally examined. On the basis of these results, a sensor and driving coils are positioned appropriately to achieve the quasi collocation. A trial servo system for this actuator experimentally confirms a wide control bandwidth beyond the mechanical resonance frequency.