An electrical power transmission system, comprising: a) an electrical power supply device, comprising: a first resonant element having inductance and capacitance; a frequency generator that generates electrical power of an electrical signal having approximately the same frequency component as a resonant frequency decided by the inductance and the capacitance and supplies the generated electrical signal to the first resonant element; and a magnetic field coupling circuit that becomes coupled by magnetic field resonance with the first resonant element, the magnetic field coupling circuit comprising a plurality of resonant elements having approximately the same resonant frequency as the resonant frequency of the resonant element, and said electrical power transmission system further comprising: b) a power receiving device including a second resonant element that receives electrical power from the power supply device by magnetic field resonance with the magnetic field coupling circuit, characterised in that the magnetic field coupling circuit is positioned at a midpoint of a distance between the first and second resonant elements (130, 330). a) an electrical power supply device, comprising: a first resonant element having inductance and capacitance; a frequency generator that generates electrical power of an electrical signal having approximately the same frequency component as a resonant frequency decided by the inductance and the capacitance and supplies the generated electrical signal to the first resonant element; and a magnetic field coupling circuit that becomes coupled by magnetic field resonance with the first resonant element, the magnetic field coupling circuit comprising a plurality of resonant elements having approximately the same resonant frequency as the resonant frequency of the resonant element, and said electrical power transmission system further comprising: b) a power receiving device including a second resonant element that receives electrical power from the power supply device by magnetic field resonance with the magnetic field coupling circuit, characterised in that the magnetic field coupling circuit is positioned at a midpoint of a distance between the first and second resonant elements (130, 330). a first resonant element having inductance and capacitance; a frequency generator that generates electrical power of an electrical signal having approximately the same frequency component as a resonant frequency decided by the inductance and the capacitance and supplies the generated electrical signal to the first resonant element; and a magnetic field coupling circuit that becomes coupled by magnetic field resonance with the first resonant element, the magnetic field coupling circuit comprising a plurality of resonant elements having approximately the same resonant frequency as the resonant frequency of the resonant element, and said electrical power transmission system further comprising: b) a power receiving device including a second resonant element that receives electrical power from the power supply device by magnetic field resonance with the magnetic field coupling circuit, characterised in that the magnetic field coupling circuit is positioned at a midpoint of a distance between the first and second resonant elements (130, 330). b) a power receiving device including a second resonant element that receives electrical power from the power supply device by magnetic field resonance with the magnetic field coupling circuit, characterised in that the magnetic field coupling circuit is positioned at a midpoint of a distance between the first and second resonant elements (130, 330).