1986年2月由欧共体理事会签署。主要内容：在1992年年底前实现商品、资本、劳务、人员自由流动的统一大市场。为了统一市场的顺利建成，改革决策机制，实行“特定多数表决制”，不再坚持过去的一致通过原则。于1987年正式生效。从总体上看，单一欧洲 法案在社会政策的决策机制上有所突破，但在将社会政策纳入欧共体法制体系方面没有什么进展。同时，在社会空间问题上仍有很多问题没有解决。此后，一些国家的政府官员及欧共体委员会的官员又不断地强调要在基本的社会权利的基础上扩展社会政策，并将其纳入欧共体的法制体系。

Apart from minor modifications, this Treaty was the first profound and wide-ranging constitutional reform of the EU since the 1950s. The SEA introduced measures aimed at achieving an internal market (for instance, harmonisation) plus institutional changes related to these (such as a generalisation of qualified majority voting and a cooperation procedure involving the European Parliament). It also provided legal form for European Political Cooperation (EPC). The SEA was signed in February 1986 and came into force on 1 July 1987.