POWER TRANSMISSION SYSTEM CAPABLE OF PREVENTING POWER TRANSMISSION EFFICIENCY FROM DEGRADING DUE TO FREQUENCY MISMATCH AND LOSS OF SYNCHRONIZATION

A code modulator transmits power to at least one code demodulator via a transmission path. The code modulator is provided with: a code modulation circuit to which output power of a power supply is supplied, the code modulation circuit modulating the output power of the power supply to generate a code-modulated wave by code modulation using a modulation code based on a code sequence, and transmitting the code-modulated wave to the code demodulator via the transmission path; and a control circuit that controls the code modulation circuit. The control circuit sets a frequency of the modulation code to a multiple of an output power frequency of the power supply.