An antenna system includes: a belt-shaped sheet portion to which a receiving antenna is detachably attached to receive information transmitted from a body-insertable apparatus introduced into a subject, the sheet portion being configured to be wrapped around and attached on a trunk of the subject； shape detection units provided on the sheet portion along a longitudinal direction of the sheet portion to detect a shape of the sheet portion； a position defining unit configured to specify an attachment position of the receiving antenna on an outer surface of the sheet portion based on the shape of the sheet portion detected by the shape detection units； and a display unit configured to display the attachment position specified by the position defining unit.
