A swing system of a construction machine having a power generation function is provided. The construction machine includes a lower driving structure capable of traveling, an upper swing structure mounted on an upper portion of the lower driving structure and provided with a working device, a swing ring gear fixed to the lower driving structure, a swing ring gear cover fixed to the upper swing structure and engaged with the swing ring gear to perform a rotational operation, a permanent magnet installed on one of the swing ring gear and the swing ring gear cover, and an induction coil installed on the other of the swing ring gear and the swing ring gear cover. Induction current is generated in the induction coil in accordance with the rotational operation of the swing ring gear cover.