Occurrence of bedsore is a serious problem in a nursing field. The purpose of this study is to develop a turning over support device in bed for preventing a bed sore. In order to support a turning over, the device worn on a human in a bed must has a light weight and flexibility. The actuator to drive such device is also required to have a light weight and flexibility. The developed device is constructed with McKibben and twist type pneumatic rubber muscles, which have above requirements. In this paper, the structure of the developed device is described, and then the experiment to verify the device is discussed. From the results, this device is effective to support a turning over since EMG with the device is decreased compared with EMG without one.