OPTICAL INFORMATION REPRODUCING DEVICE AND OPTICAL INFORMATION REPRODUCING METHOD

An optical information reproducing device is provided with a light focusing unit (8) for generating near-field light, a signal quality measuring circuit (22) for measuring reproduction signal quality of the optical information recording medium using the near-field light generated by the light focusing unit, a gap length determining circuit (17a) for determining a gap length between the light focusing unit and a surface of the optical information recording medium as a set value based on a measurement result on the reproduction signal quality in the signal quality measuring circuit, and a gap control circuit (24) for controlling a gap between the light focusing unit and the surface of the optical information recording medium based on the set value determined in the gap length determining circuit. Information is reproduced from the optical information recording medium using the near-field light generated by the light focusing unit.