A backlash detecting apparatus, comprising: a monochromator for Bragg-diffracting an incident x-ray or neutron radiation beam; an analyzer on which the beam diffracted by the monochromator is incident, the analyzer Bragg-diffracting the incident beam; a controller for controlling a driver connected to the monochromator or the analyzer so as to rotate the monochromator or the analyzer in a first direction and in a second direction opposite to the first direction; and a detector (70, 80) for detecting the beam diffracted by the analyzer or transmitted through the analyzer while the monochromator or the analyzer is rotating and measuring a backlash of the driver by using the detected beam, characterized in that the detector (70, 80) is configured to measure a first rocking curve by detecting beam while the monochromator or the analyzer is rotating in the first direction, measure a second rocking curve by detecting the beam while the monochromator or the analyzer is rotating in the second direction, and measure the backlash from a difference between a peak position of the first rocking curve and a peak position of the second rocking curve, or in that the controller is configured to rotate the monochromator or the analyzer sequentially in the first direction, in the second direction and in the first direction, and wherein the detector (70, 80) is configured to measure a first rocking curve and a second rocking curve by detecting the beam while the monochromator or the analyzer rotates in the first direction twice, and measures the backlash from a difference between a peak position of the first rocking curve and a peak position of the second rocking curve. a monochromator for Bragg-diffracting an incident x-ray or neutron radiation beam; an analyzer on which the beam diffracted by the monochromator is incident, the analyzer Bragg-diffracting the incident beam; a controller for controlling a driver connected to the monochromator or the analyzer so as to rotate the monochromator or the analyzer in a first direction and in a second direction opposite to the first direction; and a detector (70, 80) for detecting the beam diffracted by the analyzer or transmitted through the analyzer while the monochromator or the analyzer is rotating and measuring a backlash of the driver by using the detected beam, the detector (70, 80) is configured to measure a first rocking curve by detecting beam while the monochromator or the analyzer is rotating in the first direction, measure a second rocking curve by detecting the beam while the monochromator or the analyzer is rotating in the second direction, and measure the backlash from a difference between a peak position of the first rocking curve and a peak position of the second rocking curve, or in that the controller is configured to rotate the monochromator or the analyzer sequentially in the first direction, in the second direction and in the first direction, and wherein the detector (70, 80) is configured to measure a first rocking curve and a second rocking curve by detecting the beam while the monochromator or the analyzer rotates in the first direction twice, and measures the backlash from a difference between a peak position of the first rocking curve and a peak position of the second rocking curve.