A portable terminal device has a battery cover that can be opened/closed without a tool, and is small and thin, with a waterproof structure. The device has a housing with a battery pocket which houses a battery; and a battery cover which slides and opens/closes the battery pocket. The housing has a battery cover engaging section wherein a locking claw disposed on one end of the battery cover slides and is inserted such that the end of the battery cover is supported; and a packing deformation preventing/suppressing wall, which surrounds the battery pocket, except on the battery cover engaging section, and prevents a packing, integrally molded with the battery cover from deforming. The packing is integrally molded with the battery cover and a deformation preventing rib prevents the packing from deforming in the region having no packing deformation preventing/suppressing wall.