We examine how the promotion goods (offered prizes) affect to the surpluses of economic agents and the social welfare in the two-sided market, specially the newspaper industry. Though it is well known that the promotion goods hold pro-competitive effects, the offered prizes to any transaction is considered abnormal in Korea so that it is subject to the regulation in the Korea’s competition law. We point out that the promotion goods which works as the price discrimination among types of subscribers raise the subscription rate and extend the advertisement market. Hence we prove that the regulation on offering promotion goods reduces the social welfare in the two-sided market. However, the effects of offering promotion goods on consumer surpluses differ by types of subscribers. The L type subscribers whose values on the newspaper are lower than the H type’s values become better without the regulation on the promotion goods, while H types get improved with the regulation. The results of simulation shows that no regulation improves the social welfare of the two-sided market, but that it reduces the residual welfare, the social welfare minus the   surplus of subscribers and advertisers.