PURPOSE: To enable uniform wet treatment throughout the surface of a semiconductor wafer by giving a half turn to the wafer inserted in a wet treatment and setting it upside down equipment.

CONSTITUTION: A semiconductor wafer 3 is set in an orientation flat alignment unit 1 so that its orientation flat 4 will come to the upside. A cassette 2 containing the wafer 3 is taken out of the alignment unit 1 (arrow A), and immersed, from above, in chemical 6 filling a wet treatment equipment 5 (arrow B). When the semiconductor wafer 3 has been placed in the wet treatment equipment 5, a roller 7 rotates in the direction of arrow X, turning the wafer 3 in the direction of arrow Y. When a sensor 8 detects the orientation flat 4, the rotation of the roller 7 is stopped (arrow C). Thus, the wafer 3 is turned upside down. This makes uniform a time during which any portions of the semiconductor wafer 3 are under the chemical 6, enabling uniform wet treatment throughout the surface thereof.