A recording disk reproducing apparatus employing simplified digital servo control for lower-cost, more stable operational control of the apparatus. At least one of a focusing servo loop, a tracking servo loop, a spindle servo loop, and a time base servo loop employs digital conversion of an analog error signal for processing in a microprocessor. The analog-to-digital conversion circuitry has an input-output characteristic which varies in accordance with error signal level, enabling a reduction in the number of bits of A/D output necessary, and reducing cost.