The electrostatic adhesion of a charged toner particle is important for the electrophotographic process. Some models for electrostatic adhesion have been suggested. One of the models, the charge patch model, hypothecates that electrostatic adhesion force is caused by charge patches in close proximity to a substrate. It has been reported that the model fits measured data, but the experimental evidence was insufficient. We examined the relation between the charged region on a toner particle and its electrostatic adhesion by experiment. The partly charged toner particles were prepared by means of a corona discharge device, and their adhesion forces were measured using an apparatus based on vibratory detachment method. As a result, it has been verified that the slight charge in the proximity region causes most of electrostatic adhesion as mentioned by the charge patch model, and the rest of charge produces a bit of electrostatic adhesion. Additionally, it is suggested that the magnitude of electrostatic adhesion force depends on the fine charge distribution in the proximity region.