There is provided a method of performing auto white balance including: setting a plurality of sections of a whole range of a value of each of Y, Cb, and Cr in the YCbCr color space, according to a size of each value; calculating an accumulated Y, Cb, and Cr value of pixels included in each of the plurality of sections; determining effective sections according to the number of the pixels included in each of the plurality of sections; calculating a mean Y, Cb, and Cr value of pixels included in all of the effective sections by using the accumulated Y, Cb, and Cr value of each of the effective sections; calculating a mean RGB value by converting the mean Y, Cb, and Cr value into an RGB color space; and determining an RGB color gain of a Bayer image outputted from an image sensor by using the mean RGB value.