An information recording/reproducing apparatus wherein exact reproduction of both wobbled address information and sync information can be realized in a recording mode as well as in a reproduction mode. The apparatus comprises first and second detectors for detecting two diametrical side portions of each track on a recording medium where a pregroove is modulated correspondingly to address information and sync information of mutually different frequency bands; a calculator for calculating a normalized track information signal on the basis of the outputs of the first and second detectors; and a third detector for detecting the address information and/or the sync signal on the basis of the output of the calculator.