The Korean advertising market remains relatively stagnant compared to the overall size of the national economy, and with the rapid establishment of a multi-media, multi-channel environment, the shortage of advertising revenue is becoming increasingly severe. This situation clearly indicates the need for reforming advertising regulations that are unable to respond to the changing media environment, particularly the restrict on licensed media representative (media rep) companies to handling only broadcast advertising. This study conducted a stated preference survey targeting advertisers and applied a conjoint analysis to quantitatively estimate the benefits of key services provided by media rep agencies. The analysis revealed that for every KRW 100 million in advertising sales, broadcast advertising sales agencies provide advertisers with a welfare benefit of KRW 4.666 million, while digital advertising sales agencies offer a benefit of KRW 4.348 million. This suggests that if cross-media rep operations were permitted—allowing integrated sales of broadcast and digital advertising—the welfare benefits for advertisers could nearly double compared to current levels. Such a change would directly contribute to improving the efficiency of advertising transactions and revitalizing the market. Additionally, the analysis found that media planning services offer an additional benefit of KRW 3.251 million, confirming the potential for media rep to evolve beyond simple sales representatives into providers of integrated marketing solutions. The findings of this study provide policy justification for regulatory improvements aimed at expanding the domestic advertising market, enhancing the competitiveness of the advertising industry, and increasing advertiser welfare. Furthermore, it offers a foundation for discussions on the need to broaden the public service roles of media rep agencies in response to the rapidly changing digital media environment.