The diurnal polarization variation of the Earth, treated as an exoplanet with an unresolved disk but resolvable from its host star, is presented in three wavelength bands centered at 490 nm, 670 nm and 865 nm respectively according to French satellite-borne PARASOL data. We aim to estimate disk-integrated polarization of the Earth with a phase angle of 55 degrees. It is shown that: (1) the linear polarization signal and its variation are ascribed to the combination of surface feature distribution and atmospheric conditions acting as a variable polarimetric modulator; and (2) the polarimetric wavelength dependence is strong due to the atmospheric wavelength sensitivity. During the period when the PARASOL data were acquired, the cloud coverage ranged from 44.0% to 57.7%, and the polarimetric diurnal variation amplitude was within 1.8% in the 490 nm band, 1.3% in the 670 run band and 1.5% in the 865 nm band.