This paper proposes a new non-contact type chewing sensor using photo-reflector. The modulated infrared rays from the infrared LED of photo-reflector irradiate the mandible. The reflected light is received by the photo detector of photo-reflector. The chewing sensor recognizes chewing from the big movement of the mandible by chewing. By wearing the sensor in the ear, this sensor can be used in any place. The unpleasantness when using the chewing sensor is a little because the chewing sensor is non-contact type. In addition, the chewing sensor can accurately judge whether the user is chewing or not.