PURPOSE: To surely prevent substrates from slipping down by making the vertical shaft of a substrate locking means rotatable along a steeply inclined spiral groove at the same time when the shaft is moved in the vertical direction and making the locking vane of the substrate locking means rotate a substrate entrance/exit in the opening direction when a cassette is placed on a cassette placing surface and in the closing direction by its own weight when the cassette is lifted up from the surface.

CONSTITUTION: A substrate locking means 3 is composed of a vertical shaft 31 and locking vane 32. The upper and lower ends of the shaft 31 are pivotally supported with a ceiling-side and bottom-side frames 12 and 11, respectively. The shaft 31 protrudes downward from the frame 11 and can be rotated at the same time when the shaft 31 is moved in the vertical direction by means of a steeply inclined spiral groove 4 and pin 5 provided in corresponding to the frames 11 and 12. When a cassette is placed on a cassette placing surface, a locking vane 32 rotates a substrate entrance/ exit 1a in the opening direction, since the lower end of the shaft 31 is pushed up and rotated. When the cassette is lifted up from the surface, the vane 32 rotates the entrance/exit 1a in the closing direction since the shaft 31 rotationally descends by its own weight.