An apparatus includes an irradiation device configured to irradiate an object with charged particle beams, a measurement device configured to measure a characteristic of each of charged particle beams, and a controller. The measurement device includes a plate including knife edges, and a sensor configured to detect a charged particle beam incident thereon via the plate. The controller causes one charged particle beam, selected from the charged particle beams, to perform a scan relative to the measurement device so that the one charged particle beam traverses at least two knife edges among the plurality of knife edges, and to generate correction information for correcting a measurement error of the measurement device due to deformation of the plate, based on an output from the sensor upon the scan.