User information is recorded in each physical sector of an information storage medium in such a style after it is modulated according to a predetermined modulation rule. The physical sector is comprised of plural sync codes. The sync code contains a common fixed code region and variable code regions which are different depending on each sync code. The fixed code region has a sync position detecting code and this code includes a pattern in which “k+2” “0”s continue and a pattern in which 2 “0”s continue.