An address-accessing device includes first and second information generators for producing first and second information according to the received address signals; a phase offset detector for producing a phase offset according to the first and second information; a reference signal generator for producing a reference signal according to the phase offset, the first information and the second information; and a decoder used to determine the structure type of an address-in-pregroove unit (ADIP) according to the reference value. This address-accessing device is capable of adjusting the decision level and the phase offset automatically to lower the error rate occurring in the address access procedure.