1. A terminal apparatus configured to communicate with a base station using a plurality of downlink component carriers, including a primary component carrier and a non-primary component carrier, and an uplink component carrier, the terminal apparatus comprising:an extractor which, in operation, extracts a downlink control channel signal from a received signal and extracts downlink data from the received signal based on information on downlink data allocation resources;
a decider which, in operation, makes a blind decision as to whether or not control information is control information directed to the terminal apparatus, outputs the information on downlink data allocation resources for the terminal apparatus included in the control information directed to the terminal apparatus to the extractor, and identifies a Control Channel Element (CCE) to which the control information directed to the terminal apparatus is mapped;
a receiver which, in operation, receives the downlink data transmitted through at least one downlink data channel of the plurality of downlink component carriers;
an error detector which, in operation, detects presence or absence of a reception error of the received downlink data; and
a controller which, in operation, determines which Physical Uplink Control Channel (PUCCH) resource is used to transmit a response signal and which constellation point is set for the response signal based on success or failure in reception of a downlink allocation control signal in each downlink component carrier and error detection results from the error detector;
wherein when the error detection result regarding downlink data transmitted in the primary component carrier shows no error and a downlink allocation control signal is not detected in the non-primary component carrier, the controller transmits the response signal using a first PUCCH resource corresponding to the CCE identified by the decider.