To make a portable telephone set to be easily used in accordance with an application in the case of reading and wiring mail and so on in the portable telephone set.

This portable telephone set comprises an upper housing 1 having a displaying part 4, a lower housing 2 having an operating part 7 composed of an LCD 36 and a touchpad 37 and a hinge 3a and a hinge 3b for connecting the upper housing 1 and the lower housing 2 so as to make the displaying part 4 face the operating part 7. In the case the upper housing 1 and the lower housing 2 are opened wit the hinge 3a as an axis so as to make the upper and lower housings 1 and 2 to be vertically long, a CPU 33 sets a speech communication mode, displays characters and an image on the displaying part 4 and on the LCD 36 of the operating part 7 for the speech communication mode and allocates operation key functions. Meanwhile, in the case the upper housing 1 and the lower housing 2 are opened with the hinge 3b as an axis so as to make the upper and lower housings 1 and 2 to be horizontally long, the CPU 33 sets a mail mode, displays characters and an image on the displaying part 4 and on the LCD 36 of the operating part 7 for the mail mode and allocates operation key functions.