PURPOSE: To prevent the dew condensation caused by temp. difference by allowing a semiconductor element to stand by in a gaseous atmosphere having relative humidity of 13% or less for a definite period before transferring the same to the atmosphere.

CONSTITUTION: When the handling arm 21 provided in a load lock chamber 20 extends in order to receive the tray (equipped with an inspected semiconductor element and already brought to atmospheric temp., for example, -10°C) 6 reaching the position 15 on the side of an inspection part 7, this extension is detected to operate the opening and closing mechanism 22A on the side of the chamber 20 and the opening and closing mechanism 19 on the side of an airtight chamber 7a in connection with each other to open both mechanism 22A, 19. When the arm 21 having received the tray 6 is contracted to be received in the chamber 20, the mechanisms 19, 22A are automatically closed to become an airtight state. Dry air having relative humidity of 13% or less is already sent in the chamber 20 and heated by the heater embedded in the wall of the chamber 20. When the tray 6 reaches ambient temp., for example, 20°C the opening and closing mechanism 22B on the side of the selection mechanism 8 of the chamber 20 is opened to be changed over to the feed passage 25 on the side of the mechanism 8.