To provide a data transmission system preventing the interruption of a job due to line disconnection.

When data and a status indicating the data are transferred from an oversea server 11 to a domestic server 12, the domestic server 12 transmits a transmission message indicating that the data are normally transmitted to the oversea server 11. Then, when the job of the domestic server 12 is started from the oversea server 11, the domestic server 12 transmits a start message indicating that the job is started to the oversea server 11, and starts a slave job based on the started job. The oversea server 11 disconnects a line between the oversea server 11 and the domestic server 12 based on the start message. Then, when the processing of the slave job is ended, the domestic server 12 connects the line between the domestic server 12 and the oversea server 11, and transmits an end message to the oversea server 11. Thus, it is possible to prevent the interruption of the job due to line disconnection.