In an AP, a Trigger frame generator generates a trigger signal instructing an uplink signal transmission, the trigger signal including a terminal information field that includes a terminal ID subfield and a resource unit allocation information subfield, and a radio transmitter/receiver transmits the trigger signal. In a case where the trigger signal includes a first terminal information field specifying one or more contiguous resource units for random access, the Trigger frame generator sets an unused ID that is not to be used as a terminal ID in the first terminal information field.