A color adjusting method for a color light-emitting element is provided. Firstly, a first white light beam is produced by red, green and blue light-emitting units collaboratively, and a second white light beam is produced by a white light-emitting unit. Then, a second chromaticity value corresponding to the second white light beam is acquired. Then, the red, green and blue light-emitting units are controlled to produce a third white light beam according to the second chromaticity value, and a first adjusting parameter is acquired. Then, the white light-emitting unit is controlled to produce a fourth white light beam according to a third luminance value corresponding to the third white light beam, and a second adjusting parameter is acquired. Then, a gray level adjustment process is performed according to the first and second adjusting parameters.