It is advantageous for present invention to suitably determine amounts of transmission data for links in a multilink communication. In a mobile communication system (10) for making a multilink communication through which a communication is performed by using a plurality of links relayed by a plurality of base station apparatus (30), respectively, each of the base station apparatuses (30) acquire transmittable data amount information representing amounts of data able to be transmitted through the respective links by a mobile station apparatus (20) or a server apparatus (40), and the mobile station apparatus (20) or the server apparatus (40) determines amounts of transmission data to be transmitted to the respective links in correspondence to the transmittable data amount information, and transmits communication data of amounts of data corresponding to the amounts of transmission data determined to the respective links.