A wireless power transfer control method for a system including at least one power source and at least two power receivers, which wirelessly transfers power from the power source to each of the power receivers using one of magnetic field resonance and electric field resonance, comprising: a simultaneous power transfer mode in which power is simultaneously transferred to the power receivers; and a time-division power transfer mode in which power is sequentially transferred to the power receivers by time-division switching, wherein the wireless power transfer control method comprises: setting an evaluation index for each of the power receivers; and performing wireless power transfer by switching between the simultaneous power transfer mode and the time-division power transfer mode, on the basis of the evaluation index, characterised in that the evaluation index is calculated on the basis of a first index indicating a degree of coupling of electromagnetic fields in the power source and an interval between the power receivers, and a second index indicating a degree of loss of the electromagnetic fields in the power source and the interval between the power receivers, wherein power transfer is performed in the time-division power transfer mode for a power receiver, the evaluation index of which is smaller than a predetermined first set value, and power transfer is performed in the simultaneous power transfer mode for a plurality of power receivers, the evaluation indices of which are not less than the predetermined first set value, and wherein when at least three power receivers have the evaluation index that is not less than the first set value, the power receivers are classified into a group on the basis of values of the evaluation indices, and it is determined that power transfer is performed in the simultaneous power transfer mode for a plurality of power receivers within the group. a simultaneous power transfer mode in which power is simultaneously transferred to the power receivers; and a time-division power transfer mode in which power is sequentially transferred to the power receivers by time-division switching, wherein the wireless power transfer control method comprises: setting an evaluation index for each of the power receivers; and performing wireless power transfer by switching between the simultaneous power transfer mode and the time-division power transfer mode, on the basis of the evaluation index, characterised in that setting an evaluation index for each of the power receivers; and performing wireless power transfer by switching between the simultaneous power transfer mode and the time-division power transfer mode, on the basis of the evaluation index, characterised in that the evaluation index is calculated on the basis of a first index indicating a degree of coupling of electromagnetic fields in the power source and an interval between the power receivers, and a second index indicating a degree of loss of the electromagnetic fields in the power source and the interval between the power receivers, wherein a first index indicating a degree of coupling of electromagnetic fields in the power source and an interval between the power receivers, and a second index indicating a degree of loss of the electromagnetic fields in the power source and the interval between the power receivers, power transfer is performed in the time-division power transfer mode for a power receiver, the evaluation index of which is smaller than a predetermined first set value, and power transfer is performed in the simultaneous power transfer mode for a plurality of power receivers, the evaluation indices of which are not less than the predetermined first set value, and wherein when at least three power receivers have the evaluation index that is not less than the first set value, the power receivers are classified into a group on the basis of values of the evaluation indices, and it is determined that power transfer is performed in the simultaneous power transfer mode for a plurality of power receivers within the group.