A signal transmission device for transmitting a signal along a transmission path including a sinusoidal-signal transmitting unit configured to generate a sinusoidal signal that has a period the same as a period of a square-wave digital signal whose voltage level changes in correspondence with a logical value and that has a phase which differs based on change in the logical value of the square-wave digital signal, and configured to transmit the sinusoidal signal. The signal transmission device includes a sinusoidal-signal receiving unit configured to receive the sinusoidal signal, and configured to reproduce the square-wave digital signal from the sinusoidal signal based on change in the phase of the sinusoidal signal.