Provided is a sliding portable electronic device having a waterproof structure which does not restrict a circuit design. Provided is a sliding portable electronic device having a waterproof structure which does not restrict a circuit design. The sliding portable electronic device according to the present invention comprises a pair of housings engaging slidably with each other. An electric component built in one housing is connected to an electric component built in the other housing through a flexible lead. The other housing is provided with an opening, through which the flexible lead passes, and the opening is blocked by a waterproof sheet. The flexible lead, which is drawn out from the electric component of the one casing, passes between the abutment surfaces of the waterproof sheet and the other casing and is connected to the electric component of the other housing.