Provided are a base station device and a mobile station device, which can lighten a cell-search processing. The base station device (100) includes a frame constitution unit (130) for forming a frame, in which a pilot symbol multiplied by a base station scrambling code assigned to that device and a plurality of sequences contained in the corresponding sequence set is arranged in at least the head or tail, and a radio transmission unit (155) for sending the formed frame. On the receiving side of the frame, the frame timing can be detected from the position of a pilot symbol contained in that frame. Since the base station scrambling code and the sequence set containing the sequences are made to correspond to each other, candidates can be narrowed to at most the base station scrambling codes of the number of the combinations of the sequences contained in the sequence set, by detecting the sequences multiplied by the pilot symbol, so that the cell search processing can be lightened.