An electricity generating device comprises a framework, a main rotary table, an auxiliary rotary table and an electricity generating unit, wherein the main rotary table is arranged on the framework and is driven by a motor to rotate on the framework; the auxiliary rotary table is arranged on the main rotary table; the auxiliary rotary table is provided with a frame; the frame is provided with a weight set; the weight set is driven by the motor to shift on the frame left and right; the electricity generating unit is arranged on the framework; a spring is connected between the electricity generating unit and the weight set; and therefore, when the auxiliary rotary table moves to the lowest point from the highest point of the main rotary table, the spring can be driven to stretch, and after the weight set moves to an angle, the spring can elastically reset and the electricity generating unit is promoted to operate to collect energy.