A pixel binning method for processing pixel data acquired from an image sensor comprising a pixel array, the pixel binning method includes performing a first scanning process that is to scan a sensing area of the image sensor, to obtain a first number of pixel data; performing a second scanning process that is to scan the sensing area after the first scanning process is completed, to obtain a second number of pixel data; performing pixel binning on the second number of pixel data according to an offset value and an arithmetic value, wherein the offset value is determined according to the first number of pixel data.