A data management system includes: a plurality of controllers that each output control data updated by a data updating device that updates the control data and data related information to a network, the control data being data necessary for controlling a device to be controlled, the data related information being information related to the updated control data and including at least date and time information being information on a date and time when the control data are updated; and a data management device that is connected with the plurality of controllers via the network, acquires the control data and the data related information output from each of the controllers, and accumulates the control data and the data related information in association with each other.