A construction machine comprising: a prime mover; a tank that stores a hydraulic operating fluid; a hydraulic pump (7, 7a) that is driven by the prime mover and delivers, as a hydraulic fluid, the hydraulic operating fluid sucked in from the tank; a hydraulic actuator that is driven by the hydraulic fluid delivered from the hydraulic pump (7, 7a); a meter-in valve (8a1;8a6) that adjusts a flow rate of the hydraulic fluid supplied from the hydraulic pump (7, 7a) to the hydraulic actuator; a meter-in spool position adjusting device (8a2,8a2a,8a2b;8a7,8a7a,8a7b) that adjusts a spool position of the meter-in valve (8a1;8a6); and a controller that outputs a command signal to the meter-in spool position adjusting device (8a2,8a2a,8a2b;8a7,8a7a,8a7b); a velocity sensor (4a4) for sensing an operation velocity of the hydraulic actuator; and a meter-in spool position sensor (8a5;8a5;8a5b) that senses the spool position of the meter-in valve (8a1;8a6); wherein the controller has a calibration mode in which the controller derives operation characteristics that represent a relation among the spool position of the meter-in valve (8a1;8a6), the operation velocity of the hydraulic actuator, and the differential pressure across the meter-in valve (8a1;8a6) characterized in that the construction machine includes: a pressure sensor (8a3, 8a4) that senses a differential pressure across the meter-in valve (8a1;8a6); and a pressure adjusting device (7b,8b1,8b2, 40,8a6,8a7,8a7a,8a7b;8a1,8a2,8a2a,8a2b); that adjusts the differential pressure across the meter-in valve (8a1;8a6), and the controller is configured to, in a case where the spool position of the meter-in valve (8a1) has changed in a direction to increase an opening area of the meter-in valve (8a1) in the calibration mode, output a command signal to the pressure adjusting device (7b, 8b1, 8b2, 40,8a6,8a7,8a7a,8a7b;8a1,8a2,8a2a,8a2b) to reduce the differential pressure across the meter-in valve (8a1;8a6) such that an increase in the flow rate of the hydraulic fluid to be flowed into the meter-in valve (8a1;8a6) is suppressed. a prime mover; a tank that stores a hydraulic operating fluid; a hydraulic pump (7, 7a) that is driven by the prime mover and delivers, as a hydraulic fluid, the hydraulic operating fluid sucked in from the tank; a hydraulic actuator that is driven by the hydraulic fluid delivered from the hydraulic pump (7, 7a); a meter-in valve (8a1;8a6) that adjusts a flow rate of the hydraulic fluid supplied from the hydraulic pump (7, 7a) to the hydraulic actuator; a meter-in spool position adjusting device (8a2,8a2a,8a2b;8a7,8a7a,8a7b) that adjusts a spool position of the meter-in valve (8a1;8a6); and a controller that outputs a command signal to the meter-in spool position adjusting device (8a2,8a2a,8a2b;8a7,8a7a,8a7b); a velocity sensor (4a4) for sensing an operation velocity of the hydraulic actuator; and a meter-in spool position sensor (8a5;8a5;8a5b) that senses the spool position of the meter-in valve (8a1;8a6); wherein the controller has a calibration mode in which the controller derives operation characteristics that represent a relation among the spool position of the meter-in valve (8a1;8a6), the operation velocity of the hydraulic actuator, and the differential pressure across the meter-in valve (8a1;8a6) characterized in that the construction machine includes: a pressure sensor (8a3, 8a4) that senses a differential pressure across the meter-in valve (8a1;8a6); and a pressure adjusting device (7b,8b1,8b2, 40,8a6,8a7,8a7a,8a7b;8a1,8a2,8a2a,8a2b); that adjusts the differential pressure across the meter-in valve (8a1;8a6), and the controller is configured to, in a case where the spool position of the meter-in valve (8a1) has changed in a direction to increase an opening area of the meter-in valve (8a1) in the calibration mode, output a command signal to the pressure adjusting device (7b, 8b1, 8b2, 40,8a6,8a7,8a7a,8a7b;8a1,8a2,8a2a,8a2b) to reduce the differential pressure across the meter-in valve (8a1;8a6) such that an increase in the flow rate of the hydraulic fluid to be flowed into the meter-in valve (8a1;8a6) is suppressed. a pressure sensor (8a3, 8a4) that senses a differential pressure across the meter-in valve (8a1;8a6); and a pressure adjusting device (7b,8b1,8b2, 40,8a6,8a7,8a7a,8a7b;8a1,8a2,8a2a,8a2b); that adjusts the differential pressure across the meter-in valve (8a1;8a6), and the controller is configured to, in a case where the spool position of the meter-in valve (8a1) has changed in a direction to increase an opening area of the meter-in valve (8a1) in the calibration mode, output a command signal to the pressure adjusting device (7b, 8b1, 8b2, 40,8a6,8a7,8a7a,8a7b;8a1,8a2,8a2a,8a2b) to reduce the differential pressure across the meter-in valve (8a1;8a6) such that an increase in the flow rate of the hydraulic fluid to be flowed into the meter-in valve (8a1;8a6) is suppressed.