The issuance of factory license is an administrative order according to Section 5 of Administrative Procedure Act, B.E. 2539 (1996). When the tapioca starch factory is established, it may cause water pollution such as waste water and air pollution such as dust from steam boiler. These environmental pollutions may also affect health and quality of life of people living in this area. The State official shall conduct public hearing before issuing such license in compliance with rules and procedure under Factory Act, B.E. 2535 (1992), Section 30 of Administrative Procedure Act, B.E. 2539 (1996), and relating laws. The public hearing is the material process and procedure binding the State official to practice. When the State official sent a letter to the sheriff and mayor to post the notification on the issuance of tapioca starch factory license without identifying environmental problems on waste water and dust pollutions to the public, it was against the material process and procedure as prescribed by law. In addition, the State official did not conduct public hearing to restore the invalid issuance of license before the case filing, according to Section 41 paragraph one (3) of the said Act. Therefore, the issuance of tapioca starch factory license was unlawful.