In a platform business such as flea market application service, the increase of the number of sellers (buyers) induces the increase of the number of buyers (sellers) because of the cross-side network effects. Therefore, there exist problems for a platform provider whether to give more benefit to seller or buyer and how to do. This subject has not yet been fully investigated, although some researchers studied a preferential treatment method related to pricing. This study attempts to investigate an effective preferential treatment method other than pricing by analyzing user review of flea market applications.