To provide a portable telephone set capable of more exactly detecting surrounding conditions by a photosensor in the main body of the portable telephone set even when the portable telephone set is placed on a flat surface or put in a bag container.

An opening part 112 the photosensor is provided adjacently to an opening part 111 for receiver. The opening part 111 for receiver is located in a protruding part 11b protruded from a casing 10, in this case, from a surface 11a of a cover 11 and on a slope 11c formed between this protruding part 11b and the surface 11a, the opening part 112 to receive light is located.