A slewing control device for a construction machine including a slewing body and an operation unit to which an operation for slewing the slewing body is input, the slewing control device comprising: a slewing motor configured to drive the slewing body to slew; a slewing inverter configured to drive the slewing motor; a speed detection unit configured to detect an actual slewing speed of the slewing motor; an operation amount detection unit configured to detect an operation amount that is input into the operation unit; a target speed calculation unit configured to calculate a target speed according to the operation amount; a command value calculation unit configured to calculate a slewing command value to cause the actual slewing speed to reach the target speed late at a predetermined inclination; and a drive unit configured to calculate a torque command value to cause a deviation between the slewing command value and the actual slewing speed to become zero and to output the torque command value to the slewing inverter, characterized in that the drive unit is adapted to: stop outputting the torque command value regardless of the deviation in a first state where the slewing command value is equal to or greater than the actual slewing speed in a state where the operation amount detection unit detects operation input of slewing stop; and output the torque command value in a second state where the slewing command value is less than the actual slewing speed in the state where the operation amount detection unit detects the operation input of the slewing stop, and the command value calculation unit is adapted to decrease the slewing command value over time at a first inclination in the first state, and to decrease the slewing command value over time at a second inclination that is gentler than the first inclination in the second state. a slewing motor configured to drive the slewing body to slew; a slewing inverter configured to drive the slewing motor; a speed detection unit configured to detect an actual slewing speed of the slewing motor; an operation amount detection unit configured to detect an operation amount that is input into the operation unit; a target speed calculation unit configured to calculate a target speed according to the operation amount; a command value calculation unit configured to calculate a slewing command value to cause the actual slewing speed to reach the target speed late at a predetermined inclination; and a drive unit configured to calculate a torque command value to cause a deviation between the slewing command value and the actual slewing speed to become zero and to output the torque command value to the slewing inverter, characterized in that the drive unit is adapted to: stop outputting the torque command value regardless of the deviation in a first state where the slewing command value is equal to or greater than the actual slewing speed in a state where the operation amount detection unit detects operation input of slewing stop; and output the torque command value in a second state where the slewing command value is less than the actual slewing speed in the state where the operation amount detection unit detects the operation input of the slewing stop, and the command value calculation unit is adapted to decrease the slewing command value over time at a first inclination in the first state, and to decrease the slewing command value over time at a second inclination that is gentler than the first inclination in the second state. stop outputting the torque command value regardless of the deviation in a first state where the slewing command value is equal to or greater than the actual slewing speed in a state where the operation amount detection unit detects operation input of slewing stop; and output the torque command value in a second state where the slewing command value is less than the actual slewing speed in the state where the operation amount detection unit detects the operation input of the slewing stop, and the command value calculation unit is adapted to decrease the slewing command value over time at a first inclination in the first state, and to decrease the slewing command value over time at a second inclination that is gentler than the first inclination in the second state.