Mechanically ultraflexible and stretchable devices are expected to open new possibilities in fields of biomedical applications as well as wearable electronics. Especially, conformability, ruggedness, lightweight, biocompatibility, and large-area are all important to create new electronic applications that can be directly mounted on the surface of human skins and/or even inside the body. From this viewpoint, ultraflexible organic thin-film devices, such as organic photovoltaic cells, organic light-emitting diodes, and organic thin-film transistors integrated circuits, have attracted much attention recently. In this talk, we report our recent progress of ultraflexible organic thin-film devices that are manufactured on ultrathin plastic film with the thickness of 1 μm. We will also describe their emerging applications, remaining issues and future prospects.