To provide a wireless transmission system and a communication terminal whereby a user of a mobile station apparatus performs seamless communication when an area of a wireless LAN system exists in an area of a cellular system.

A server 191 transmits video information comprising basic data and supplemental data to a router 100 via the Internet 192. The router 100 distributes the basic data to a BS 110 of the cellular system 193 and the supplemental data to an AP 120 of the wireless LAN system 194. The BS 110 transmits the basic data to an MS 150 and the AP 120 transmits the supplemental data to the MS 150. When the MS 150 exists in the area of the cellular system 193, the MS 150 maintains a communication channel with the BS 110 at all times, and when the MS 150 enters the area of the wireless LAN system 194, the MS 150 further opens a channel with the AP 120 depending on a state while keeping the channel with the BS 110.