A construction machine having a swing structure, comprising: an engine; a hydraulic pump which is driven by the engine; the swing structure; a first electric motor and a hydraulic motor which drive the swing structure; a swing operation lever which is operated by an operator to drive the swing structure; a second electric motor which assist-drives the hydraulic pump during motoring and generates electric energy during drive using the engine; an electric storage device which stores electric energy to be supplied to the first and second electric motors (25, 23); and a controller which receives a signal corresponding to an operation amount and an operation direction on the swing operation lever and controls charge and discharge in the electric storage device, characterized in that the controller stores, for an amount of electricity stored in the electric storage device, an upper limit value and a lower limit value of a normal use region which is an optimal use range of the electric storage device, a regeneration prohibition value which is set to be larger than the upper limit value of the normal use region and to be smaller than a maximum amount of electricity stored in the electric storage device, and a swing prohibition value which is set to be smaller than the lower limit value of the normal use region and to be larger than a minimum amount of electricity stored in the electric storage device; and when the amount of electricity stored in the electric storage device is in the normal use range, the controller drives and brakes the swing structure in accordance with the operation amount and the operation direction on the swing operation lever using both the first electric motor and the hydraulic motor; when the amount of electricity stored in the electric storage device exceeds the upper limit value of the normal use range and reaches the regeneration prohibition value, the controller drives and brakes the swing structure in accordance with the operation amount and the operation direction on the swing operation lever using only the hydraulic motor while motoring the second electric motor so as to consume the electric energy stored in the electric storage device; and conversely when the amount of electricity stored in the electric storage device falls below the lower limit value of the normal use range and reaches the swing prohibition value, the controller drives and brakes the swing structure in accordance with the operation amount and the operation direction on the swing operation lever using only the hydraulic motor while using the engine to drive the second electric motor so as to charge the electric storage device. a hydraulic pump which is driven by the engine; the swing structure; a first electric motor and a hydraulic motor which drive the swing structure; a swing operation lever which is operated by an operator to drive the swing structure; a second electric motor which assist-drives the hydraulic pump during motoring and generates electric energy during drive using the engine; an electric storage device which stores electric energy to be supplied to the first and second electric motors (25, 23); and a controller which receives a signal corresponding to an operation amount and an operation direction on the swing operation lever and controls charge and discharge in the electric storage device, characterized in that the controller stores, for an amount of electricity stored in the electric storage device, an upper limit value and a lower limit value of a normal use region which is an optimal use range of the electric storage device, a regeneration prohibition value which is set to be larger than the upper limit value of the normal use region and to be smaller than a maximum amount of electricity stored in the electric storage device, and a swing prohibition value which is set to be smaller than the lower limit value of the normal use region and to be larger than a minimum amount of electricity stored in the electric storage device; and when the amount of electricity stored in the electric storage device is in the normal use range, the controller drives and brakes the swing structure in accordance with the operation amount and the operation direction on the swing operation lever using both the first electric motor and the hydraulic motor; when the amount of electricity stored in the electric storage device exceeds the upper limit value of the normal use range and reaches the regeneration prohibition value, the controller drives and brakes the swing structure in accordance with the operation amount and the operation direction on the swing operation lever using only the hydraulic motor while motoring the second electric motor so as to consume the electric energy stored in the electric storage device; and conversely when the amount of electricity stored in the electric storage device falls below the lower limit value of the normal use range and reaches the swing prohibition value, the controller drives and brakes the swing structure in accordance with the operation amount and the operation direction on the swing operation lever using only the hydraulic motor while using the engine to drive the second electric motor so as to charge the electric storage device.