In a coding system wherein an error correction/detection coding is
combined with a synchronization recovering technique using a
synchronization code, the problems of a pseudo synchronization and a step
out due to error detection are solved. There is provided a coding part
212 for coding an input multiplexed code string 201 to an error
correcting/detecting code comprising an information bit and a check bit,
and code string assembling part 213 for inserting a synchronization code
into any one of a plurality of periodically predetermined synchronization
code inserting positions in the code string 201, for arranging the
information bit at an optional position in the code string, and for
arranging the check bit at a position other than the synchronization code
inserting positions in the code string 201 to assemble an output code
string 205.