An antenna unit includes: an external body; a display unit which is provided on one side of the external body and displays information; an antenna which is provided on the other side of the external body and is disposed to face the display unit at an interval therebetween; an internal body which accommodates the antenna and is movable with respect to the external body toward a side opposite to the display unit. The external body has a belt connecting section which protrudes toward the side opposite to the display unit. The internal body protrudes from the external body by moving toward the side opposite to the display unit. The internal body protrudes farther from the external body than the belt connecting section from the external body.