This paper describes 5 1/4-in. high track-access performance magneto-optic disk drive. The drive employs a split optical system with a swing-arm actuator, the inertia of which is 160 g cm2(equivalent to a linear actuator of 10 g weight). An avarage seek time was estimated less than 35ms in the absence of latency. It is noticeable that both its mechanism and control systems are very simple.