An electronic device includes a transmission unit that transmits a transmission wave from a transmission antenna; a reception unit that receives, from a reception antenna, a reflected wave of the transmission wave; a controller that detects an object that reflects the transmission wave; a power supply device that supplies electric power to at least any of the foregoing components; and a substrate having the foregoing components thereon. The transmission and reception antennas are disposed on a first surface of the substrate. The controller and the power supply device are disposed on a second surface of the substrate opposite to the first surface. The substrate includes a waveguide that guides the transmission wave and/or the reflected wave between the first and second surfaces and is covered with an electromagnetic wave shielding member apart from the second surface by a distance of ¼ of a wavelength of the transmission or reflected wave.