Diffuse scattering observed from X-ray or neutron scattering experiments contains information about static and thermal disorder of atoms in crystal. The diffuse scattering theory with correlated thermal vibration of atoms can explain the oscillatory background profile of diffracted intensities by neutron scattering experiment of crystals with ordered arrangement of atoms. Rietveld refinement analysis is a well-known method to analyze structure of material from its diffraction pattern. Former Rietveld analysis uses Legendre series to fit the profile of background intensities. We can perform new background function using diffuse scattering theory with correlated thermal vibration of atoms in Rietveld analysis to analyze diffracted intensities of some powder materials. Using this new background function, the information about thermal disorder in crystal can be obtained.