行政機關於從事各種行政行為時，應本於其職權，運用各種調查方法，取得證據，再透過評價形成心證，以釐清事實並作成最終之決定。有關行政機關從事調查及適用證據法則之規定，向來不受行政機關之重視，尤其與證據有關之原理原則，更少見有深入之探討者。此外，有關取得證據及釐清事實之方法，本於職權調查主義，由行政機關裁量決定之。至於有那些被容許之調查方法，現行法中，較為重要者，可見於行政程序法，於該法第39條至第42條分別列舉出四種調查方法，即通知陳述意見、要求提供文書等、送請鑑定及進行勘驗。此外，尚有涉及證人之規定。本文乃以該法為探討之中心，針對相關之條文規定，分別就證據及各種不同之調查方法依序論述之，最終並提出檢討及修法之建議。

It depends on the correct facts to make correct decisions for administrative agency. So it is necessary for administrative agency to clean facts, and administrative agency will valuate to form the opinions to make decisions.In Taiwan, the codes of administrative investigation is not available until now, but spreads on different areas of laws and regulations. The articles 36-43 of the administrative process law are the general regulations of administrative investigation of the facts and evidence.The articls36 of the administrative process law is the ”administrative authority investigation”. While administrative authority investigation concerns about different means and responsibilities of investigations, it is necessary to understand the connotations of it. Secondly, it is the duty of administrative agency to invest the different kinds of evidence, but it still has the limitation.To clarify the concept and the range of the administrative authority investigation, this thesis consists of several points below: first of all, this thesis would like to establish the concept of administrative authority investigation, and doing necessary researches of administrative authority investigation. Secondly, this thesis would analyze the indispensable standards as ”evidence necessary” ”principle of proportionality” ”Duty of cooperation” etc. This thesis would also analyze the recent judgments of the Supreme Administrative Court. We hope we could offer some advises to advance the fragments of laws in our country.