A portable telephone in which two bodies thereof are placed in superposed relation, and one body slides relative to the other body to change how far they superpose, thus expanding and contracting the overall length of the telephone in the sliding direction. The one body can pull out relative to the other body with an area left where a part of the one body is superposed on the other body in the extended state. Engaging members, i.e. engaging pawls and sliders, that serve as a rotation preventing mechanism for preventing the two bodies from relative rotating are intensively provided in the superposed area within the extended state.