Triboelectric energy harvesters are expected as a power source for self-powered wearable devices since they can generate electricity from the low-frequency motion of the human body. For wearable device applications, high stretchability is required to follow the dynamic three-dimensional surface of the human body. We have realized a stretchable sheet-shaped triboelectric energy harvester with a high output and elasticity. The high output has been achieved by a fluorine plasma treatment for the surface of the dielectric layer. We demonstrate a self-powered signal transmitter and LED-embedded gloves, exploiting the characteristics of the harvester. Furthermore, we propose a highly efficient intermittent operation circuit to drive electronic devices, using a small amount of power generated by the harvester. Our study can contribute to solve the problem of power source limitations in wearable electronics.