This research focuses on the relationship between lobbying regulation and public transparency in OECD 34 membership countries. It addresses three main questions: Is there an overall tendency for the countries which have legislated lobbying regulations to show a higher level of transparency than the countries which have not? What do the current lobbying regulation frames contain? What reforms need to be adopted for enhancing lobbying transparency? On the first question, statistically negative and insignificant outcomes were drawn. The mean and median of transparency index values in the 15 member countries which regulated lobbying were lower than in the non-regulation 19 countries. The t-test and regression analyses also showed statistically insignificant results. These statistical results externally seemed contradictory to conventional perception. However, in considering both the typical lobbying regulation frame, which included disclosure of information on lobbying activities, and the positive arguments in previous studies, it seems unreasonable to discount the potential positive impact of the regulation. On the second question, a comparative examination of the current legal frames was conducted. I organized a 2 by 2 table by using two dimensions, (1) whether the countries legislated their lobbying regulation (2) transparency level of the countries. The results were basically arranged by eight categories, such as definition of lobbyist, registration, disclosure, sanctions, revolving door provision. From the examination some general arguments were identified: The lobbying regulations were initiated in response to the repeated corruption scandals in each country. These events generated public pressure for lobbying regulation, in turn triggering legislators' discussion on the introduction of regulation. The critical moment for such legislation was met when significant political changes occurred, such as elections, democratization or growth of civil societies. To answer the third question, reform for enhancing lobbing transparency, the contradictory views on lobbying regulation were reviewed. Then, the 34 members were classified into high, medium, and low sections by both transparency ranking values and timelines of the initiation of regulations. Following the divisions, some general directions for reform were suggested. Finally, I added more specific discussions concerning enlargement of public disclosure and compliance with of lobbying regulations.