行政權與司法權係兩個獨立且相互制衡的運轉機制，警察既隸屬於內政部，復又必須接受檢察官的指揮偵查，故警察任務與職權分屬行政與司法性質乃勢所必然，本文首先探討其危害防止和刑事追訴的本質。再者，行政權與司法權的界限，在警察行使職權時，卻呈現出判斷上及分類上的困難，是為警察雙重功能措施，需予以辨明，此屬於分的層次；反之，刑事訴訟法卻出現「得使用強制力，不得逾越必要程度」的字眼，遭到有否符合法治國明確性原則的質疑，又強制力的種類、強制執行的其他要件，均有深究的必要，這屬於合的範疇。本文於討論上述問題時，均分別指出我國法律制定上、及法律概念上值得商榷之處，並提出判準之道；最後，於文末簡評兩則案例加以印證。 Executive power and judicial power are two independent mechanisms that check and balance each other under the concept of the separation of powers. While the police is subordinate to the Ministry of Interior, according to the Code of Criminal Procedure, it is subject to the investigations of prosecutors. In this research, the nature of deterrence of danger on executive power and litigation of criminal on judicial power are first discussed. Due to the diverse nature of both executive power and judicial power, difficulties on judgment and classification often occur when the police exercise their power. Hence, the dual functions of police should be clarified to resolve the conflicts. However, the Code of Criminal Procedure states that ＂... may be arrested by force ..., but such force may not be excessive.＂ The statement has attracted criticism due to its relatively ambiguous definition which violates the principle of clarity of a Legal state. In addition, it is necessary to clarify the different types of force as well as other essential conditions regarding the forced exercise of law. This research aims to discuss the nature of task and duty of police on administration and judicature, the discrimination and combination on deterrence of danger, and the litigation of criminal. Several guidelines on the legislation of law as well as legal concept in Taiwan are also addressed in this research. Two cases studies are further provided to validate the argument stated in this research.