139 sync blocks, each having 111 bytes, are disposed on each track of a magnetic tape. Among the 139 sync blocks, 121 sync blocks each consist of a two-byte detection pattern for detecting the sync block, three-byte identification information for identifying the sync block, 96-byte main data, and 10-byte inner error correcting code added to the identification information and the main data. In the remaining 18 sync blocks, instead of the main data, 96-byte outer error correcting code is included. The outer error correcting code is provided for each group of the 139 sync blocks. Such a group of 139 sync blocks is obtained by dividing 2224 sync blocks contained in sixteen tracks by sixteen planes, 1668 sync blocks contained in twelve tracks by twelve planes, or 1112 sync blocks contained in eight tracks by eight planes. The sync blocks are arranged on the magnetic tape so that the distance between the sync blocks belonging to the identical plane is constant among the planes.