PURPOSE: To provide an inexpensive, applicable hydraulic servo device which has a simple structure to be easily applied to existing facilities and serves high-speed performance, high precision and high response.

CONSTITUTION: Servo valves 1, 2 of at least two large, small types which have flow property are arranged in parallel. On the way of servo current instructions or opening instructions from a control section 5 to servo valves 1, 2, function generators 7, 8 with the property corresponding to the magnitude of an instruction signal or a filter with a frequency band different therefrom are provided. Individual servo currents or opening instructions are made adjustable, high-speed performance is controlled by the large flow servo valve 1 and high precision and high response are controlled by the small flow servo valve 2. As a result, an inexpensive hydraulic servo device can be provided, which has no deterioration of the large flow servo valves 1, 2 and still serves high-speed performance, high precision and high response.