There is provided for a calibration method for an operation apparatus. The operation apparatus comprises a first moving body unit capable of pivoting about a horizontally extending axis, a first driving unit configured to drive the first moving body unit, and a first detection unit configured to detect a pivot position of the first moving body unit. The method comprises aligning the first moving body unit to one reference position selected from a plurality of predetermined reference positions, determining the reference position by comparing a driving parameter value of the first driving unit at the one reference position with determination parameter values respectively preset for the plurality of reference positions, and registering, as reference position information for calculating the pivot position, position information of the one reference position determined in the determining and detection value information of the first detection unit.