Nowadays, a low birthrate and longevity are proceeding in developed countries. Due to the low birthrate and longevity, there is a shortage of caregivers. Therefore, an assistance of nursing care is necessary. Also, according to a multidisciplinary advance of robots, robots increase opportunities for operating in environment in which human intervene. Operating a robot in human presence is a dangerous for human. Therefore, a signal transmission between human and robots is necessary. This paper uses a cuff of sphygmomanometer as an interface of signal transmission. This interface is attached to an arm of user and an air pressure of interface is controlled to constant. An error between pressure command and response caused by a muscle bulge of user is regarded as an intention of user. An integration of error is given to a manipulator as a position command. According to this system, the interface user can operate a position of manipulator based on the user's intention.