The invention relates to the technical field of photovoltaic power generation, in particular to a sun tracking device for photovoltaic power generation. The sun tracking device is characterized in that a pile and a sleeve type structure combination is adopted, a winch drives a steel wire rope to pull a plurality of unpowered passive tracking supports to rotate to track change of solar azimuth; an dip angle adjusting mechanism can be arranged to enable a photovoltaic module board to rotate around a horizontal axis to track changes of solar elevation angle; a mirror reflecting board is arranged on the lower border of the photovoltaic module board to enhance light harvesting energy of the photovoltaic module board. The turn-off feature of the steel wire rope is utilized, and plane arrangement and elevation arrangement of the tracking supports are high in flexibility and quite adaptable to block foundations with irregular planes and land conditions with uneven sites; various deformation of the steel wire rope is consumed and compensated by the aid of a gravity tensioning balancer, and stable operation of a transmission system is sustained; the sun tracking device is high in cost performance, suitable for largescalization design of the supports and high in capability of fitting for complicated project conditions.