An apparatus for detecting relative positioning information between rolls, comprising: a subject position fix unit mounted on a subject roll that is the reference of measurement and discharging a laser signal to a measurement roll to be measured; a relative position measurement unit mounted on the measurement roll to be measured and receiving the laser signal from the subject position fix unit; and a detection result output unit that receives information about the laser signal from the relative position measurement unit, calculates the alignment state of the measurement roll with respect to the subject roll, and outputs the alignment state to a display, wherein the relative position measurement unit includes: a first laser receiver that receives a first laser signal from the subject position fix unit; a second laser receiver that receives a second laser signal from the subject position fix unit; and a third laser receiver that reflects and receives the first laser signal discharged from the subject position fix unit, wherein the third laser receiver includes: a received-laser signal reflection module that passes and reflects the first laser signal discharged from the subject position fix unit such that the passed first laser signal is radiated to the first laser receiver and the reflected laser signal generated by reflection is radiated to a reflected-laser signal reception module; the reflected-laser signal reception module to which the reflected laser signal is radiated; and a reflected-laser signal sensor module that stores the reflected laser signal radiated to the reflected-laser signal reception module into data, and wherein the alignment state of the measurement roll with respect to the subject roll is output to the display in real time on the basis of data transmitted from the relative position measurement unit. wherein the relative position measurement unit includes: a first laser receiver that receives a first laser signal from the subject position fix unit; a second laser receiver that receives a second laser signal from the subject position fix unit; and a third laser receiver that reflects and receives the first laser signal discharged from the subject position fix unit, a first laser receiver that receives a first laser signal from the subject position fix unit; a second laser receiver that receives a second laser signal from the subject position fix unit; and a third laser receiver that reflects and receives the first laser signal discharged from the subject position fix unit, wherein the third laser receiver includes: a received-laser signal reflection module that passes and reflects the first laser signal discharged from the subject position fix unit such that the passed first laser signal is radiated to the first laser receiver and the reflected laser signal generated by reflection is radiated to a reflected-laser signal reception module; the reflected-laser signal reception module to which the reflected laser signal is radiated; and a reflected-laser signal sensor module that stores the reflected laser signal radiated to the reflected-laser signal reception module into data, and wherein the alignment state of the measurement roll with respect to the subject roll is output to the display in real time on the basis of data transmitted from the relative position measurement unit. a received-laser signal reflection module that passes and reflects the first laser signal discharged from the subject position fix unit such that the passed first laser signal is radiated to the first laser receiver and the reflected laser signal generated by reflection is radiated to a reflected-laser signal reception module; the reflected-laser signal reception module to which the reflected laser signal is radiated; and a reflected-laser signal sensor module that stores the reflected laser signal radiated to the reflected-laser signal reception module into data, and wherein the alignment state of the measurement roll with respect to the subject roll is output to the display in real time on the basis of data transmitted from the relative position measurement unit.