An electronic device capable of transmitting and receiving a mail through an internet usually has from 12 to 20 operation keys inclusive of numerical keys and special keys. In order to input Japanese characters inclusive of “kanji” and special characters as data, complex operations must be executed by changing over the input mode. A portable data terminal as represented by a cellular phone or an electronic device such as a data terminal as represented by a personal computer or a desk top telephone, has such a shape that the first center line of the first housing and the second center line of the second housing come into agreement and in parallel with each other only in a state where the first housing and the second housing are folded by the hinge.