A magnetic single-component development process in electrophotography has interesting characteristics on a magnetic and electrostatic interaction of toner particles. Magnetic force restrains toner adhesion to non-image area and this feature enhances the development. However, long chains made by magnetic interaction force between magnetic toner particles deteriorate toner-image quality on the photoreceptor. It is known from a past experimental study that the magnetic chain length is influenced not only by the magnetic field but also by the electrostatic charge of toner particles. Furthermore, configuration of toner image formed was measured in a magnetic single-component development process of electrophotography by a 3D non-contact measurement system that consists of a laser displacement meter and an x-y stage. The density distribution of toner particles on a photoreceptor measured by this system was compared with macroscopic measurement and the numerical analysis calculated by the Distinct Element Method. These results showed good agreement each other.