A radio base station apparatus having an improved cell search performance in a scalable bandwidth system. A base station (100) can flexibly assign communication bandwidths of terminals from support bandwidths included in cell bandwidths that are the greatest ones, which are used by the base stations, of support bandwidths supported by a scalable bandwidth system. The base station (100) comprises a frame forming part (160) that forms a frame in which the pattern of a frame synchronization sequence (P-SCH), which is placed in a predetermined one, having a smallest support bandwidth, of bands of cell bandwidths, differs according to the cell bandwidths; an IFFT part (170) that serves as a frame transmitting means for transmitting the foregoing frame; a GI inserting part (180); and a radio transmitting part (190).