It is difficult to talk with others for the person who has a severe physical and utterance disability. Especially in outside, the difficulties increase on and it becomes a hard barrier for social participation. Although several communication aids instruments are already in market, there are almost no aid instrument for whole-body palsy patients. In this study, we developed a small portable communication aid instrument based on PDA, for the cerebral palsy patient, which can be controlled with only one switch. The aid instrument has a phrase book that has phrase collections for user's every day needs, and it has note function that user can write character by character. We evaluated the usability of the instrument, we found that the instrument that has two input method (phrase book and note function) decreased input time and can express any messages. In addition, from trial usage of a target user, we also found that it facilitates rapid conversation in everyday typical cases and it also facilitates flexible communication.