專利法上之「先使用權」即專利法第 59 條第 1 項第 3 款，其規定專利權效力不及於「申請前已在國內實施，或已完成必須之準備者」，但先使用權人限於在其「原有事業目的範圍內繼續利用」。「先使用權」在保障系爭專利申請日前已經實施系爭專利的個體其繼續利用系爭專利之權，亦保障實施系爭專利而生之物品的後續流通或使用權益，此已為 2013 年專利法所肯定的法理。本文回顧過往的司法判決，並指出大致與 2013 年專利法之理念相同，但少數判決在「先使用」之認定上有問題。此外，本文亦針對未明確的法律議題提出實務建議，例如針對「原有事業目的範圍」，其範圍雖不限於系爭專利申請前之事業規模，但應侷限在先使用權人「預期所得繼續生產、利用之規模及範圍」。

“Prior user right” under the Patent Act is vested in Article 59, Paragraph 1, Subparagraph 3, which provides that a patent right does not extend to a person who had practiced the patented invention or been ready to do so before the filing date of the patent, but such person may continue to practice the patented invention only within the original business scale. Under the new legislative intent of the 2013 Amendment, the prior user right protects the interest of a person who began to use the patented invention before the filing date of the patent and allows such person to continue the use. Any future exploitation of a product made by such person will not be stopped by the patentee. This paper reviews the past judicial decisions related to the prior user right and concludes that most decisions comply with the new legislative intent. But, there are some uncertain issues that need to be discussed. This paper will proposes some solutions to those unresolved issues.