An OFDM transmitter and receiver realizing high-speed cell search and having a reducible circuit scale. An OFDM transmitter includes an SCH inserting section for constructing a frame where a synchronization sequence in a predetermined position from the head of a first sub-frame is arranged and a synchronization sequence composed of the symbols of the former synchronization sequence and the symbols whose I, Q components are interchanged is arranged in a predetermined position from the head of a second sub-frame adjacent in the time-axis direction to the former sub-frame, an IFFT section, a P-SCH conversion section, and an RF transmitting section for transmitting this frame. Thus, the receiving end of the frame can locate the position of either synchronization sequence and determine the frame timing from that position, thereby increasing the speed of the cell search.