The present disclosure relates to a wireless power transfer method, a wireless power transfer apparatus, and a wireless charging system in a wireless power transfer field, and there is provided a communication method of a wireless power transmitter performing communication with at least one wireless power receiver through a plurality of slots, and the method may include allocating any one of the plurality of slots to any one of the at least one wireless power receiver, providing at least one of the plurality of slots to the any one wireless power receiver as locked slots subsequent to the allocation, and receiving information associated with a configuration phase and information associated with a negotiation phase from the any one wireless power receiver within the locked slots.