When a charged body passes by the front of an ungrounded metal box such as a box of electronic equipment, an electrostatically induced voltage is generated. The induced voltage can cause malfunctions and failure of the equipment. However, whether a voltage is induced in the metal box by a moving charged body and how much is induced is not clear. In this study, measured induced voltages are compared with values calculated for two capacitance-measuring methods. The results will be helpful to estimate the possibility of malfunction and failure by induced voltage and whether a standard test method should be considered.