Tax investigation is a dynamic administrative process. Through the administrative process regulated by The Administrative Procedures Act in Taiwan, it can be divided into at least four stages: beginning, preparation, proceeding and rights remedy. How should the procedures of the Administrative Procedure Act be applied in the preceding stages regarding Internal Revenue Taxes and Duties? In addition to the Administrative Procedures Act, The Taxpayer Rights Protection Act and Tax Collection Act also stipulated related procedures. How should they be applied at each stage of the tax investigation to meet the requirements of the due process in administrative procedures? Through reviewing what the due process in administrative procedures that the tax investigation should be followed at each stage by examining the administrative process, this article intends to present the requirements of the due process in administrative procedures of the tax investigation at specific stage on the basis of the Administrative Procedures Act, The Taxpayer Rights Protection Act and Tax Collection Act.