To rotate a rotary body at a constant velocity, a swing control device 50 of an electric rotary excavator controls the rotation of the rotary body with a small first torque command value Tl. Thus, when inertia moment of the rotary body is changed due to extension or retraction of a boom and an arm, the change of the inertia moment affects the rotation velocity of the rotary body, and an operator can perform a rotation operation with the same feeling as in a hydraulically-driven excavator. In contrast, when operating a swing lever 10 for acceleration, the rotation is controlled with a large second torque command value T2. Accordingly, a good and quick operational feeling is obtained without a delay in acceleration or deceleration, and the degradation of workability can be avoided.
