A data converter, a signal transmission method, and a signal transmission system for transmitting a signal to a programmable logic controller are provided. The data converter: performs sampling multiple times with respect to data detected by a sensor in one communication period of communication with a programmable logic controller; acquires statistical data by statisticizing a plurality of sampling data in the one communication period; and transmits the statistical data to the programmable logic controller when the one communication period is reached. Therefore, a signal sampling density is improved, and thus control accuracy can be enhanced. At the same time, a data transmission amount of a bus is reduced, a load on the programmable logic controller is reduced, and user convenience is improved.