We have studied the dynamics of toner and carrier particles in a two-component development system used for electrophotography in order to improve the image defect due to the bead-carry-out (BCO) phenomenon. We have manufactured a mock-up apparatus consisting of a pseudo-photoreceptor drum, development sleeve, and stationary magnetic roller. We have measured the number density of carrier particles adhered to the photoreceptor surface after the development process and have observed the behavior of the toner and carrier particles using a high-speed color microscope camera. It has been confirmed that the number density of the adhered carrier particles increases when the DC development voltage is high, toner concentration is low, and speed ratio of the development sleeve to photoreceptor drum is low. It has been observed that depletion of toner particles from the tips of carrier chains occurs in the post-nip region of the development area. It is assumed that when the initial toner concentration is lower than the threshold value, 6 wt%, insulative toner particles do not affect the electrical conduction of the conductive carrier chains, and therefore, the electrical charge at the top of the chains, which is induced by the applied voltage, increases. This increase in the electrical charge causes an increase in the Coulomb force applied to the top of the chains, and the BCO phenomenon occurs. On the other hand, when the speed of the development sleeve is low, the number of toner particles developed on the latent image is not sufficient to neutralize the surface potential of the latent image. The effective voltage between the sleeve and photoreceptor drum is not sufficiently reduced in this case, and thus, the BCO phenomenon occurs.