A signal output device, in a signal level non-transition period, matches an output impedance of an output section to a characteristic impedance of an output transmission path, and also matches the output impedance of the output section to the characteristic impedance of the output transmission path in a signal level transition period in a case in which a second bit of output-target data is a first value, and generates a mismatch between the output impedance of the output section and the characteristic impedance of the output transmission path in the signal level transition period in a case in which the second bit of the output-target data is a second value, so as to cause generation of a change in waveform in an output signal in the signal level transition period such that an absolute value of a signal level of the output signal exceeds a preset threshold value.