A signal transmission system has a master node and plural slave nodes performing data transmission with the master node. The master node has a serial-to-parallel converter for converting a serial data signal from each slave node into a parallel data signal. Each slave node has a transmission aligner for performing word alignment processing upon a parallel data signals, and a parallel-to-serial converter for converting the parallel data signal subjected to the word alignment processing by the transmission aligner into a serial data signal, and outputting the serial data signal to the master node.