A signal transmission apparatus including: a plurality of modulating sections configured to modulate a transmission object signal; and a plurality of demodulating sections configured to demodulate the modulated signals modulated by the modulating sections, wherein each of carrier frequencies as frequencies different from each other used by respective sets of the modulating sections and the demodulating sections is set such that frequency of a third-order intermodulation distortion component generated on a basis of two carrier frequencies adjacent to each other is not present within any of reception bands of modulated signals based on each of the other carrier frequencies.