「一行為不二罰原則」係在禁止國家對於人民之同一行為，以相同或類似之措施多次的處罰，經大法官釋字第五○三號解釋後，已可確立為現代民主法治國家之基本原則。對於違反行政法上義務者，應依法處罰，惟以往行政機關裁處之行政罰，其處罰名稱、種類不一，裁處程序及標準互異，常生困擾，復因處罰性質的不同，行政機關常有併罰的情形。行政罰法制定後，使行政罰之解釋與適用有一定之原則與標準可資遵循，故如何加強相關概念之探討，實有其重要意義。本文以一行為不二罰之理論為基礎，探討一行為不二罰之內涵及適用，藉供交通執法時之參考。

Ne bis in idem means that no same action shall be punished twice or more. Based on the Interpretation No. 503 by the Grand Justice, it is now a basic principle in the democratic country, Taiwan. Those who violate the administrative law should be punished, but the existing punishments vary widely in titles, types, procedures, and standards. Also, the punishments may be combined due to different features. The establishment of the administrative punishment law provides a principle and standard to interpretation and application of administrative punishment. Therefore, it should be further studied. This paper discusses the content and application of ne bis in idem for reference to administration of law.