This paper describes a novel bed sensing method for unconstrained detection of body movement and scratching motion through biosignal measurement. The bed sensing method can be used to monitor a person's health condition at home or in the hospital. Moreover, this system is able to detect the frequency of scratching motion. Conventional methods that use infrared cameras or acceleration sensors impose physical and/or psychological stress on the patient. We have developed an unconstrained biosignal bed sensing device using piezoceramics. Piezoceramic sensors are bonded to stainless steel plates sandwiched between the floor and the four legs of the bed. The sensors accurately detect body movement and scratching motions through the acquisition and measurement of biosignals. The device is suitable for various health applications including monitoring of sleep and diseases characterized by itching.