A hydraulic circuit for a construction machine comprising: operation means; a controller for outputting a command current based on an operation amount of the operation means; an electromagnetic proportional pressure reducing valve actuated by the command current outputted from the controller; and a hydraulic pilot type spool valve actuated by a secondary pressure of the electromagnetic proportional pressure reducing valve, the spool valve being adapted to change a pump pressure in response to a change in an opening area of the spool valve; wherein as a correction processing for correcting characteristics of a proportional valve command value which is a current value given to the electromagnetic proportional pressure reducing valve and of the opening area of the spool valve, the controller is configured to detect an actual proportional valve command value (I1a, I1b) at a time of obtaining a set pump pressure (Pt) which has been set in advance, compare the actual proportional valve command value (I1a, I1b) to a theoretical proportional valve command value (I0a, I0b) at which the set pump pressure is to be obtained in the case that a tolerance of the secondary pressure with respect to the proportional valve command value does not exist, and then perform a correction to compensate for a difference between the both command values, characterized in that with respect to the pump pressure, an inflection point, at which a rate of increase of the pump pressure (Pt) to a change of the proportional valve command value starts to decrease, is set, and the controller is configured to perform the correction based on a comparison of the actual proportional valve command value when the set pump pressure which is a pump pressure at the inflection point is obtained and the theoretical proportional valve command value when the set pump pressure which is a pump pressure at the inflection point is obtained. operation means; a controller for outputting a command current based on an operation amount of the operation means; an electromagnetic proportional pressure reducing valve actuated by the command current outputted from the controller; and a hydraulic pilot type spool valve actuated by a secondary pressure of the electromagnetic proportional pressure reducing valve, the spool valve being adapted to change a pump pressure in response to a change in an opening area of the spool valve; wherein as a correction processing for correcting characteristics of a proportional valve command value which is a current value given to the electromagnetic proportional pressure reducing valve and of the opening area of the spool valve, the controller is configured to detect an actual proportional valve command value (I1a, I1b) at a time of obtaining a set pump pressure (Pt) which has been set in advance, compare the actual proportional valve command value (I1a, I1b) to a theoretical proportional valve command value (I0a, I0b) at which the set pump pressure is to be obtained in the case that a tolerance of the secondary pressure with respect to the proportional valve command value does not exist, and then perform a correction to compensate for a difference between the both command values, characterized in that with respect to the pump pressure, an inflection point, at which a rate of increase of the pump pressure (Pt) to a change of the proportional valve command value starts to decrease, is set, and the controller is configured to perform the correction based on a comparison of the actual proportional valve command value when the set pump pressure which is a pump pressure at the inflection point is obtained and the theoretical proportional valve command value when the set pump pressure which is a pump pressure at the inflection point is obtained.