MU-MIMO is implemented with little changes in the mechanism of the DCF. There is provided a wireless terminal station apparatus that is used in a wireless communication system formed of one wireless base station apparatus and a plurality of wireless terminal station apparatus, in which grouping is performed on the wireless terminal station apparatus in such a way that the wireless terminal station apparatus belongs to any one of a plurality of groups, and the wireless terminal station apparatus includes a backoff controlling portion that performs control such that a backoff value at the time of random backoff, the backoff value of the wireless terminal station apparatus belonging to at least one group, is selected from a set of candidates for a backoff value which is a set of values formed of predetermined limited numbers.