Electrospinning is a versatile and straightforward method for the formation of continuous thin fibers and is based on an electrohydrodynamic process from polymer solutions and melts. To improve the throughput of electrospinning and the quality of the electrospun thin fibers, an in-depth understanding of the fiber formation process is required. In the present study, we attempted to quantitatively analyze the bending instability of an electrified thin jet during electrospinning. The electrified-jet flying phenomenon from the spinneret to the substrate was investigated by high-speed camera observation and electromagnetic and kinetic analyses, i.e., the flying velocity of the electrified jet was measured, and the electric potential was obtained from finite element method analysis of an electric field. The charge density and diameter of the electrified jet in the bending instability region during electrospinning were determined by solving the equation of motion.