A terminal apparatus configured with one or more downlink component carriers the terminal apparatus comprising: a control information detecting section which, in operation, detects control information transmitted from a base station on one or more control channel elements, CCEs, wherein the control information including downlink assignment information that indicates a resource for downlink data, the resource being assigned to each of the downlink component carriers; a decoding section which, in operation, decodes the downlink data, which is transmitted in the resource indicated by the downlink assignment information included in the detected control information; a control section which, in operation, determines constellation points used for a response signal for the decoded downlink data and an uplink control channel resource used for the response signal depending on an error detection result regarding the downlink data in a first downlink component carrier and a second downlink component carrier included in the configured downlink component carriers; and a transmitting section which, in operation, transmits the response signal using the determined constellation points and the uplink control channel resource, wherein: when control information corresponding to downlink data on the first downlink component carrier is detected and control information corresponding to downlink data on the second downlink component carrier is not detected, the response signal is transmitted using a first uplink control channel resource, an index of which is associated with a smallest index of the CCEs on which the control information is transmitted; and when control information corresponding to downlink data on the second downlink component carrier is detected and control information corresponding to downlink data on the first downlink component carrier is not detected, the response signal is transmitted using a second uplink control channel resource, an index of which is notified from the base station. a control information detecting section which, in operation, detects control information transmitted from a base station on one or more control channel elements, CCEs, wherein the control information including downlink assignment information that indicates a resource for downlink data, the resource being assigned to each of the downlink component carriers; a decoding section which, in operation, decodes the downlink data, which is transmitted in the resource indicated by the downlink assignment information included in the detected control information; a control section which, in operation, determines constellation points used for a response signal for the decoded downlink data and an uplink control channel resource used for the response signal depending on an error detection result regarding the downlink data in a first downlink component carrier and a second downlink component carrier included in the configured downlink component carriers; and a transmitting section which, in operation, transmits the response signal using the determined constellation points and the uplink control channel resource, wherein: when control information corresponding to downlink data on the first downlink component carrier is detected and control information corresponding to downlink data on the second downlink component carrier is not detected, the response signal is transmitted using a first uplink control channel resource, an index of which is associated with a smallest index of the CCEs on which the control information is transmitted; and when control information corresponding to downlink data on the second downlink component carrier is detected and control information corresponding to downlink data on the first downlink component carrier is not detected, the response signal is transmitted using a second uplink control channel resource, an index of which is notified from the base station. when control information corresponding to downlink data on the first downlink component carrier is detected and control information corresponding to downlink data on the second downlink component carrier is not detected, the response signal is transmitted using a first uplink control channel resource, an index of which is associated with a smallest index of the CCEs on which the control information is transmitted; and when control information corresponding to downlink data on the second downlink component carrier is detected and control information corresponding to downlink data on the first downlink component carrier is not detected, the response signal is transmitted using a second uplink control channel resource, an index of which is notified from the base station.