A signal transmission device includes a first master signal conversion circuit and at least one first slave signal conversion circuit. The first master signal conversion circuit is configured to receive first partial data of output data from a data generation unit, convert the first partial data of the output data into a first transmission signal correspondingly, and output a first synchronization signal. The at least one first slave signal conversion circuit is configured to receive at least second partial data of the output data and convert the at least second partial data of the output data into at least one second transmission signal correspondingly, wherein the at least one first slave signal conversion circuit controls a timing of the at least one second transmission signal according to the first synchronization signal.