An antenna device which is built into an electronic appliance having a metal cover provided with a radio wave passer is provided. The electronic apparatus includes an antenna portion arranged adjacent to the radio wave passer so as to be capable of transmitting and receiving radio waves through the radio wave passer. A reflecting portion which reflects the radio waves radiated from the antenna portion is located on an opposite side of the antenna portion, so that the antenna portion is between the reflecting portion and the radio wave passer.