This paper proposes a new concept of a combined and a shared screen for new small devices called GDA (Group Digital Assistant). In GDA, the screens of two PDAs can be treated just as one screen in combination view mode and can be shared in sharing view mode. GDA uses a wireless LAN and Bluetooth for radio communication. We have developed application software for an idea generation support system on GDA and experimented in cooperative work for evaluation. We found that functions of GDA were effective in actual cooperative work. The concept of GDA can permit usage of a cellular phone and a PDA in the next generation.