A base station used in a mobile communication system, the base station comprising: a channel generating unit configured to generate synchronization channels to be used in a cell search performed by a user equipment; and a transmitting unit configured to wirelessly transmit a signal including the synchronization channels, wherein the synchronization channels include a primary synchronization channel (P-SCH) for detecting a reception timing and a secondary synchronization channel (S-SCH) including cell ID group information; the secondary synchronization channel (S-SCH) is composed of a combination of different short codes selected from multiple combinations of short codes; correspondence between the combinations of short codes and the cell ID group information is predefined; the combinations of short codes are determined such that secondary synchronization channels including a same short code are not transmitted from adjacent cells at two or more of frame synchronization timings in succession; the secondary synchronization channel (S-SCH) is composed of a first short code identified by a first index number and a second short code identified by a second index number; and the combinations of short codes are predetermined for each cell ID group information such that a condition "the second index number - the first index number ≤ Δ, Δ being an integer less than or equal to 29," is satisfied, wherein a numerical range of 0-30 is predefined as index numbers, and the first index number and the second index number are selected from the same numerical range of 0-30 both for a first one of the frame synchronization timings and a second one of the frame synchronization timings. a channel generating unit configured to generate synchronization channels to be used in a cell search performed by a user equipment; and a transmitting unit configured to wirelessly transmit a signal including the synchronization channels, wherein the synchronization channels include a primary synchronization channel (P-SCH) for detecting a reception timing and a secondary synchronization channel (S-SCH) including cell ID group information; the secondary synchronization channel (S-SCH) is composed of a combination of different short codes selected from multiple combinations of short codes; correspondence between the combinations of short codes and the cell ID group information is predefined; the combinations of short codes are determined such that secondary synchronization channels including a same short code are not transmitted from adjacent cells at two or more of frame synchronization timings in succession; the secondary synchronization channel (S-SCH) is composed of a first short code identified by a first index number and a second short code identified by a second index number; and the combinations of short codes are predetermined for each cell ID group information such that a condition "the second index number - the first index number ≤ Δ, Δ being an integer less than or equal to 29," is satisfied, wherein a numerical range of 0-30 is predefined as index numbers, and the first index number and the second index number are selected from the same numerical range of 0-30 both for a first one of the frame synchronization timings and a second one of the frame synchronization timings.