Disclosed is a smaller and lighter stage device which can be applied to a device such as a length measurement SEM for inspecting and/or evaluating a semiconductor, and in which the effect of a magnetic field on an electron beam can be reduced. Linear motors 110, 111, 112, 113 are disposed on four sides of a base 104 to be distanced from an electron beam projection position (the center of the stage device), respectively. The base 104 has dimensions substantially equivalent to minimum dimensions determined by the size of a top table 101 and a movable stroke. Linear motor stators 110, 112 are configured to have a “C-shaped” structure whose opening faces outside of the stage device, respectively. Further, a movable table is coupled to the top table via linear guides 107, 109 composed of a nonmagnetic material or roller mechanisms composed of a nonmagnetic material.