A white balancing method includes capturing an original image with red (R), green (G) and blue (B) color channels; computing and converting the R, G and B color channels into original color histogram; stretching the original color histograms over the entire grayscale width from 0 to 255 values; and adjusting a color of the original image based on the stretched color histograms to obtain a white balanced image. In the computing and converting the original color histograms, a sampling length follows a formula of spanm=min{(2h, H), (2w, W)}, wherein h=[log2 H]+1, w=[log2 W]+1, H represents a height of the original image, W represents a width of the original image, [ ] is the Gaussian symbol, ( ) is greatest common divisor function, and min{ } means selecting the minimum value. An image capturing device using the white balancing method is also provided.