A construction machine comprising: a swing structure; a hydraulic motor for driving the swing structure; an electric motor for driving the swing structure and being mechanically connected to the hydraulic motor; a hydraulic pump being driven by a prime mover and for supplying hydraulic fluid to the hydraulic motor; an operating device configured to instruct the swing structure to make a swing motion; and a control device configured to, when demanded torque necessary for the swing motion of the swing structure instructed by the operating device can be produced by the electric motor alone, control an output torque of the electric motor in such a manner that meter-out and meter-in pressures of the hydraulic motor that is run together with the electric motor approach each other, or in such a manner that the meter-out pressure is larger than the meter-in pressure, wherein the demanded torque necessary for the swing motion of the structure instructed by the operating device is determined based on operation amount of the operating device and the actual rotation speed of the swing structure, characterized in that when the swing structure is accelerating in a fine operation region where the operation amount of the operating device is equal to or less than a reference value, or when the actual rotation speed of the swing structure is constant regardless of the operation amount of the operating device, the control device, with maintenance of the delivery rate of the hydraulic pump at a predetermined value, controls the output torque of the electric motor such that the meter-out and meter-in pressures approach each other, or such that the meter-out pressure is larger than the meter-in pressure. a swing structure; a hydraulic motor for driving the swing structure; an electric motor for driving the swing structure and being mechanically connected to the hydraulic motor; a hydraulic pump being driven by a prime mover and for supplying hydraulic fluid to the hydraulic motor; an operating device configured to instruct the swing structure to make a swing motion; and a control device configured to, when demanded torque necessary for the swing motion of the swing structure instructed by the operating device can be produced by the electric motor alone, control an output torque of the electric motor in such a manner that meter-out and meter-in pressures of the hydraulic motor that is run together with the electric motor approach each other, or in such a manner that the meter-out pressure is larger than the meter-in pressure, wherein the demanded torque necessary for the swing motion of the structure instructed by the operating device is determined based on operation amount of the operating device and the actual rotation speed of the swing structure, characterized in that when the swing structure is accelerating in a fine operation region where the operation amount of the operating device is equal to or less than a reference value, or when the actual rotation speed of the swing structure is constant regardless of the operation amount of the operating device, the control device, with maintenance of the delivery rate of the hydraulic pump at a predetermined value, controls the output torque of the electric motor such that the meter-out and meter-in pressures approach each other, or such that the meter-out pressure is larger than the meter-in pressure.