An antenna apparatus configured to receive a wireless signal transmitted from a capsule endoscope introduced into a subject, the antenna apparatus comprising: a substrate that is bendable; an antenna unit (41, 42, 43, 44, 45, 46, 47, 48) that is mounted on the substrate and is configured to receive the wireless signal; an electronic device (41b, 42b, 43b, 44b, 45b, 46b, 47b, 48b) that is mounted on the substrate and connected to the antenna unit (41, 42, 43, 44, 45, 46, 47, 48) to perform a predetermined process on the wireless signal received by the antenna unit (41, 42, 43, 44, 45, 46, 47, 48); and a sealing structure characterized in that the sealing structure is configured to seal the electronic device (41b, 42b, 43b, 44b, 45b, 46b, 47b, 48b), wherein the sealing structure has: a plate portion (91, 92) that is formed with a harder material than the substrate and interposes the electronic device (41b, 42b, 43b, 44b, 45b, 46b, 47b, 48b) via the substrate between a top surface and a back surface of the substrate on which the electronic device (41b, 42b, 43b, 44b, 45b, 46b, 47b, 48b) is mounted; the plate portion having a first plate portion that is positioned on the top surface side of the substrate and a second plate portion that is positioned on the back surface side of the substrate and an elastic body that is provided on an outer periphery of the plate portion (91, 92) to cover a part of the first and second plate portions (91, 92) and integrally molded so as to press the first and second plate portions (91, 92) against the substrate. a substrate that is bendable; an antenna unit (41, 42, 43, 44, 45, 46, 47, 48) that is mounted on the substrate and is configured to receive the wireless signal; an electronic device (41b, 42b, 43b, 44b, 45b, 46b, 47b, 48b) that is mounted on the substrate and connected to the antenna unit (41, 42, 43, 44, 45, 46, 47, 48) to perform a predetermined process on the wireless signal received by the antenna unit (41, 42, 43, 44, 45, 46, 47, 48); and a sealing structure characterized in that the sealing structure is configured to seal the electronic device (41b, 42b, 43b, 44b, 45b, 46b, 47b, 48b), wherein the sealing structure has: a plate portion (91, 92) that is formed with a harder material than the substrate and interposes the electronic device (41b, 42b, 43b, 44b, 45b, 46b, 47b, 48b) via the substrate between a top surface and a back surface of the substrate on which the electronic device (41b, 42b, 43b, 44b, 45b, 46b, 47b, 48b) is mounted; the plate portion having a first plate portion that is positioned on the top surface side of the substrate and a second plate portion that is positioned on the back surface side of the substrate and an elastic body that is provided on an outer periphery of the plate portion (91, 92) to cover a part of the first and second plate portions (91, 92) and integrally molded so as to press the first and second plate portions (91, 92) against the substrate. a plate portion (91, 92) that is formed with a harder material than the substrate and interposes the electronic device (41b, 42b, 43b, 44b, 45b, 46b, 47b, 48b) via the substrate between a top surface and a back surface of the substrate on which the electronic device (41b, 42b, 43b, 44b, 45b, 46b, 47b, 48b) is mounted; the plate portion having a first plate portion that is positioned on the top surface side of the substrate and a second plate portion that is positioned on the back surface side of the substrate and an elastic body that is provided on an outer periphery of the plate portion (91, 92) to cover a part of the first and second plate portions (91, 92) and integrally molded so as to press the first and second plate portions (91, 92) against the substrate.