Computed tomography (CT) has been used to obtain 3D data from an object or patient. However, most of CT uses polychromatic energy and that results in beam hardening artifact. Therefore, many methods for correcting beam hardening were proposed. Linearization method and post reconstruction method are main category of beam hardening correction method. Especially empirical approaches were commonly used at linearization method; however, empirical methods do not guarantee the linearity of projection data because it uses reconstructed image to decide linearity. Therefore, corrected images are not monochromatic CT images because we could not specify the energy. Proposed method use linearization method as a basic concept. However, we had considered about the relationship between path length and projection data and then found a way to specify the energy of corrected images because proposed method linearizes the projection data fundamentally. Moreover, calculation time for making corrected sinogram was very short. Therefore, this method can be used practically.