A control system of a multichannel optical switch suppressing the generation of a leakage current in a multichannel, highly integrated EO-SW to enable stable operation, that is, a control system of a multichannel optical switch using devices having an EO effect wherein an electrode voltage application device applies voltage for switching optical switch devices based on switching data when judging that an elapsed time from when the switching data has started to be output from a path switching instruction device is shorter than a predetermined counted time threshold and the electrode voltage application device applies voltage for switching based on the switching data only when a switching judgment processing device judges that predetermined switching conditions have been met when judging that the elapsed time has been exceeded and does not apply voltage for switching to the switch devices and sends a switching failure notice to a path switching instruction device from the switching judgment processing device when judging that predetermined switching conditions have not been met.