A base station apparatus is disclosed in which control section (150) generates an index indicating a response signal resource to be used for transmission of a response signal in response to downlink data of a plurality of CCs for at least each second CC, and transmitting section (160) transmits control information including the index. When a terminal receives the control information using only one second CC or two or more CCs among the plurality of CCs, the terminal apparatus determines the response signal resource based on the index of the second CC. Control section (150) specifies, as the response signal resource, using the index of the second CC, a first resource for transmission of a response signal in response to downlink data transmitted using only one CC or a second resource for transmission of a plurality of response signals in response to downlink data transmitted using a plurality of CCs.