A hydraulic control apparatus for a construction machine in which a hydraulic actuator is connected to a hydraulic pump via a directional control valve of a closed center type, and in which an unloading valve, which is connected to a tank, is provided between the directional control valve and the hydraulic pump the hydraulic control apparatus comprising: an unloading valve controlling part configured to control the unloading valve such that fluid communication between the hydraulic pump and the tank is blocked in a situation where the directional control valve is in such a state that a fluid path to the hydraulic actuator is opened, and such that the fluid communication between the hydraulic pump and the tank is established in a situation where the directional control valve is in such a state that a fluid path to the hydraulic actuator is closed; a command value calculating part configured to operate under the situation where the directional control valve is in such a state that the fluid path to the hydraulic actuator is opened, wherein the command value calculating part is configured to: calculate, based on an operation amount of an operation member (40, 42, 44) for changing a position of the directional control valve and a discharge pressure (p d) of the hydraulic pump, a virtual negative control pressure (p n) in a virtual bleed system, the virtual bleed system comprising a virtual directional control valve (V1, V2, V3) of an open center type and a virtual negative control restriction disposed downstream from the virtual directional control valve (V1, V2, V3) in a center bypass line, the virtual negative control pressure (p n) being a back pressure in the center bypass line due to the virtual negative control restriction, and calculates a control command value for the hydraulic pump based on the virtual negative control pressure (p n) such that a discharge flow rate of the hydraulic pump is decreased or increased in accordance with an increase or decrease of the virtual negative control pressure (p n); and a correcting part configured to operate under the situation where the directional control valve is in such a state that the fluid path to the hydraulic actuator is closed, wherein the correcting part is configured to correct the control command value or a parameter, which is used in calculating the control command value, such that the discharge flow rate of the hydraulic pump is a predetermined flow rate. an unloading valve controlling part configured to control the unloading valve such that fluid communication between the hydraulic pump and the tank is blocked in a situation where the directional control valve is in such a state that a fluid path to the hydraulic actuator is opened, and such that the fluid communication between the hydraulic pump and the tank is established in a situation where the directional control valve is in such a state that a fluid path to the hydraulic actuator is closed; a command value calculating part configured to operate under the situation where the directional control valve is in such a state that the fluid path to the hydraulic actuator is opened, wherein the command value calculating part is configured to: calculate, based on an operation amount of an operation member (40, 42, 44) for changing a position of the directional control valve and a discharge pressure (p d) of the hydraulic pump, a virtual negative control pressure (p n) in a virtual bleed system, the virtual bleed system comprising a virtual directional control valve (V1, V2, V3) of an open center type and a virtual negative control restriction disposed downstream from the virtual directional control valve (V1, V2, V3) in a center bypass line, the virtual negative control pressure (p n) being a back pressure in the center bypass line due to the virtual negative control restriction, and calculates a control command value for the hydraulic pump based on the virtual negative control pressure (p n) such that a discharge flow rate of the hydraulic pump is decreased or increased in accordance with an increase or decrease of the virtual negative control pressure (p n); and calculate, based on an operation amount of an operation member (40, 42, 44) for changing a position of the directional control valve and a discharge pressure (p d) of the hydraulic pump, a virtual negative control pressure (p n) in a virtual bleed system, the virtual bleed system comprising a virtual directional control valve (V1, V2, V3) of an open center type and a virtual negative control restriction disposed downstream from the virtual directional control valve (V1, V2, V3) in a center bypass line, the virtual negative control pressure (p n) being a back pressure in the center bypass line due to the virtual negative control restriction, and calculates a control command value for the hydraulic pump based on the virtual negative control pressure (p n) such that a discharge flow rate of the hydraulic pump is decreased or increased in accordance with an increase or decrease of the virtual negative control pressure (p n); and a correcting part configured to operate under the situation where the directional control valve is in such a state that the fluid path to the hydraulic actuator is closed, wherein the correcting part is configured to correct the control command value or a parameter, which is used in calculating the control command value, such that the discharge flow rate of the hydraulic pump is a predetermined flow rate.