To simply inexpensively inspect laser beam characteristics without mounting a scanning optical unit in real equipment.

The method for inspecting laser beam characteristics of a scanning optical unit 4 for optically scanning a laser beam comprises the steps of scanning an optical lattice 6 having a lattice formed in a scanning direction of a laser beam 5 by the beam of the unit 4 to be inspected, receiving the beam intensity-modulated by the lattice 6 by receiving means 7, 8, converting the beam into an electric signal, extracting a maximum value and a minimum value of each one period in a change of a sine wave state of the signal in the scanning region of the beam 5, differentiating one or more of sequential data of the maximum value, sequential data of the minimum value, and sequential data calculated from the sequentially adjacent maximum and minimum values, and inspecting the presence or absence of a discontinuous fault of the beam characteristics based on its result.