For strict application of food hygiene regulation such as hazard analysis - critical control point system, the development of rapid and simple measurement scheme for biological particles is essential. Recently, a hybrid method using dielectrophoretic manipulation and micro fluidic operation has attracted attention for the bioparticle detection. However, the influence of electrode structure on the dielctrophoretic force has not been fully understood. For effective design of dielectrophoretic devices, it is important to investigate quantitatively the capture characteristics. In the present work, we numerically simulated the particle dynamics in the capture region of a dielectrophoretic micro device with interdigitated electrodes. The dependence of dielctrophoretic force on the electrode width and gap length showed that there was the maximum of capture height of particles for adequate electrode structure. Furthermore, the number of captured particles was accurately evaluated in consideration of the effective region ratio. Under typical condition, the number of captured particles almost agreed with the experimental result.