An apparatus for inspecting an internal circuit of a semiconductor device is provided, wherein an inspection table having an inspection equipment such as a microscope, a positioner or the like mounted thereon is constructed into a vibration-proof structure. On a frame surrounding a tester is horizontally supported an inspection table through air spring structures arranged on four corners of the frame, so that vibration or shock produced from a floor or the tester may be effectively absorbed by the air spring structures, to thereby be prevented from adversely affecting a semiconductor device to be inspected. Also, the semiconductor device is set on a socket of a socket-equipped board arranged above the tester in a manner to be close proximity to the tester, so that a substantially true signal may be obtained.