Disclosed are a novel sunshade device for a balcony and an operation method thereof. The novel sunshade device comprises a guiding support (11) fixedly mounted at the outer side end of the top wall of the balcony and a sunshade plate (8) which can slide in a guiding groove (12) of the guiding support (11), thus, when the sunshade plate (8) slides rightward to the rightmost side along the guiding groove (12), sun shading and rain shielding can be conducted on the balcony, and when the sunshade plate (8) slides leftward to the leftmost side along the guiding groove (12), sunlight is allowed to irradiate in the balcony. By using the device, the state of the sunshade plate can be adjusted according to the weather, when rain shielding or sun shading is needed, the sunshade plate can extend out, so that the situation that rain drops into the balcony or sun irradiates in the balcony is avoided; and when the irradiation area of the sun needs to be increased, the sunshade plate can retract, and accordingly the balcony can have the largest irradiation area.