A signal transmission device including: a differential signal transmission unit having two output terminals for outputting a differential signal to a paired signal lines including first and second signal lines; a single-ended signal transmission unit having two output terminals for outputting independent two-channel single-ended signals to the paired signal lines; and a filter unit having first and second common mode filters. One terminal of the differential signal transmission unit and one terminal of the single-ended signal transmission unit are connected to the first signal line via one inductor of the first common mode filter of the filter unit. The other one terminal of the differential signal transmission unit and the other one terminal of the single-ended signal transmission unit are connected to the second signal line via one inductor of the second common mode filter of the filter unit.