An information recording medium comprising: a first region in which type identification information for identifying a type of the information recording medium is recorded by recesses and/or protrusions which are formed by a given modulation method and whose lengths are longer than a length of an optical system resolution limit of a playback device; a second region in which content data is recorded by recesses and/or protrusions which are formed by the given modulation method and which include a recess and/or a protrusion whose length is shorter than the length of the optical system resolution limit, a blank region between the first region and the second region, wherein the first region contains first address information recorded therein in a first address data format, the second region contains second address information recorded therein in a second address data format that differs from the first address data format, and the blank region is constituted by a group of recesses and/or protrusions in which no significant information other than an address is recorded, wherein a region of the blank region which is closer to the first region is provided with recesses and/or protrusions which are formed by the given modulation method, whose lengths are longer than the length of the optical system resolution limit, and which are suited to the first address data format, and a region of the blank region which is closer to the second region is provided with recesses and/or protrusions which are formed by the given modulation method, which include a recess and/or a protrusion whose length is shorter than the length of the optical system resolution limit, and which are suited to the second address data format. a first region in which type identification information for identifying a type of the information recording medium is recorded by recesses and/or protrusions which are formed by a given modulation method and whose lengths are longer than a length of an optical system resolution limit of a playback device; a second region in which content data is recorded by recesses and/or protrusions which are formed by the given modulation method and which include a recess and/or a protrusion whose length is shorter than the length of the optical system resolution limit, a blank region between the first region and the second region, wherein the first region contains first address information recorded therein in a first address data format, the second region contains second address information recorded therein in a second address data format that differs from the first address data format, and the blank region is constituted by a group of recesses and/or protrusions in which no significant information other than an address is recorded, wherein a region of the blank region which is closer to the first region is provided with recesses and/or protrusions which are formed by the given modulation method, whose lengths are longer than the length of the optical system resolution limit, and which are suited to the first address data format, and a region of the blank region which is closer to the second region is provided with recesses and/or protrusions which are formed by the given modulation method, which include a recess and/or a protrusion whose length is shorter than the length of the optical system resolution limit, and which are suited to the second address data format.