在日本，傳統社會福利服務的供給以政府為主，提供高齡者等相關的協商援助、設施服務與居家服務等。然而邁入21世紀，公私部門間的關係出現顯著的變化，政策執行逐漸依賴民間組織，兩者間的權責劃分越來越模糊，連社會福利服務供給也不例外。準市場是一種活用市場原理，同時保留公部門管制的制度設計。該理論強調「購買者與供應者分離」，認為財政與供給應分別歸屬公部門和私部門，同時也主張服務的使用者可以藉由選擇權的行使，從多樣的服務供給者中選擇自己所需的服務。本文從準市場理論的成功要件和評估基準來檢視日本介護保險制度的成果與課題。研究發現，日本介護保險制度準市場化後，雖然介護服務市場結構轉換，但尚未形成實質競爭的市場，介護服務市場雖有多元供給者，卻因禁止價格競爭，以及供給者集中在少數大型業者而影響其成效。另外，購買者即是使用者的制度設計，恐怕更容易引起資訊不對稱，從而影響選擇權的發揮。

In Japan, social welfare services are traditionally provided by the government, which support the elderly with counseling, facility support and home care services. However, entering the 21st century, there has been a significant change in the relationship between the public and private sectors, with policy implementation gradually relying on the private sector. The role and responsibility between the public and private sectors has become vague, including the supply of social welfare. The quasi-market is an alternative to the free market mechanism, which at the same time preserves the control and institutions of the public sector. Quasi-market theory stresses “the separation of supplier and purchaser”, meaning that the finance and the supply should be the responsibilities of the public and private sectors respectively. Service users may choose what they need according to the various services offered. This study aims to review the results of Japan’s Long-term Care Insurance System through the success factors and evaluation criteria of quasi-market theory. Th study finds that the structure of long-term care services changed after the quasi-marketization of Japan’s Long-term Care Insurance System, however it is not yet a competitive free market. Though there are multiple suppliers in the long-term care industry, forbidding price competition and the fact that only large companies have provided such services has limited the success of the quasi-market mechanism. Additionally, the design of having service users act as purchasers causes asymmetric information and negatively affects the power of choice.