An apparatus for changing optical disks including a plurality of driving shafts, supported on the bottom plate of an optical disk drive, and a plurality of elastic devices. The driving shafts rotate synchronously around their vertical axes to raise and lower the trays. Each of the driving shafts includes a thread region, threads of which can be engaged with the trays, and an upright region located on the thread region. The pitch for threads in the upper thread portion is larger than that in the lower thread portion of the thread region. Each of the elastic devices has one end fixed to a top end of the upright region of the corresponding driving shaft or fixed beneath the top plate, and the other end provided together with the flat surface between the upright region and the thread region for clamping the trays in the range of the upright regions. Trays are also forced by the elastic devices by rotating the driving shafts to move along the thread from the position held at the upright region to that held at the thread region.