Energy harvesting technologies are defined as a converting ambient energy into electric energy. Among these technologies, triboelectric nanogenerator (TENG) is a promising method which converts mechanical energy into electric energy. However, some existing TENGs are hard to be used in the practical application field, because they have complicated structure and instantaneous output. In this paper, we introduce an innovative and simple freestanding type roly-poly TENG (RP-TENG) that can sustainably harvest mechanical energy from oscillating motions. RP-TENG is mainly composed of the hemisphere shell with attached electrode and base plate with another attached electrode. The principal mechanism of RP-TENG is that it oscillates like a roly-poly motion when the hemisphere shell is tilted to any direction. At that time, electric potential is continuously generated owing to coupling effect of triboelectrification and electrostatic induction between the hemisphere shell and base plate. Simple structure makes manufacturing process simple and maintenance easy while working principle that gains sustainable output is quite simple. Because prototype of RP-TENG gains multiple oscillations from one input, another distinguished advantage of RP-TENG is multiple electricity output, experimentally measured 17, gained from just a single input. It suggests that users can use RP-TENG properly in desired condition by adjusting oscillation duration time. Furthermore, it can be widely used as self-powered acceleration sensor, which indicates orientation and quantity of acceleration, owing to sustainable output and energy harvesting possibility in all directions. For this purpose, we construct meshed cells on the base plate in rows numbering cells. When hemisphere shell is oscillated by external input, we sense electric measurements between contact cells and non-contact cells during duration time. With these advantages, we expect RP-TENG to be used as an energy harvesting device or self-powered sensors that can be easily used in various situations.