In order to clear the activated area in electrostatic accelerator facilities, four accelerator facilities were selected and typical neutron emission experiments were performed. Neutron flux during operation and induced activity caused by charged particles on the accelerator and its surrounding area after irradiation were measured. Also the monitored neutron flux and calculated value by Monte Carlo calculation using PHITS code were compared. It was confirmed that the results between calculated data and measured data showed the good agreement with each other. Finally, it was concluded that we have to take care the activation of beam line and target. But, it is not necessary to treat accelerator tank, surrounding materials, and building concrete as radioactive materials in case of decommissioning.