Abstract: A hole inspection lens unit to inspect inside a hole formed in a workpiece including a tubular outer tube; a tubular inner tube inserted into the outer tube; an objective lens disposed in a tip end of the inner tube; a mounting unit to support proximal ends of the outer tube and the inner tube where a camera to image the inside of the hole through the objective lens is attached. Light emitting diodes disposed inside the outer tube and around the inner tube and a tubular light guide tube emit light to diffuse the light into the hole. An annular spacer with gas passages disposed between the light guide tube and outer peripheral surface of the inner tube and an inner peripheral surface of the outer tube communicate with an annular gas passage opens at the tip ends of the outer tube and the inner tube.