Presented here is a method of mass renormalization where the radiation field is quantized in term in the mass energy of the particle. With quantization carried out in the form of harmonic expansion, it becomes possible to do mass renormalization using the usual method of perturbation in terms of the quantized form of the vector potential. This method contains the mass correction due to the quantized radiation field for the electron. It gives only finite values and is, therefore, free from singularities.