According to the present invention, a hydraulic control apparatus for construction machinery comprises: hydraulic pumps (11, 12); first and second control valve units which control the flow directions of working oil discharged from the hydraulic pumps (11, 12) to supply the working oil to first and second work machines, respectively, and which control the degree of opening of flow channels which interconnect the first and second work machines and the hydraulic pumps (11, 12), respectively; and a control unit (70) which controls the first and second control valve units in accordance with operating signals inputted from first and second operating units. The control unit (70) determines whether the current work mode is a general work mode or a preferential work mode, and if the mode is determined to be a general work mode, calculates a first degree of opening of a normal channel in accordance with the operating signal inputted from the first operating unit and outputs the calculated first degree of opening of a normal channel to the first control valve unit, and if the mode is determined to be a preferential work mode, calculates a second degree of opening of a normal channel in accordance with the operating signal input from the second operating unit, outputs the calculated second degree of opening of a normal channel to the second control valve unit, and outputs a control signal to the second control valve unit such that the degree of opening of the second control valve unit is smaller than the first degree of opening of a normal channel, so as to preferentially ensure the flow of the working oil being supplied to the first work machine.