A wafer container includes a container body, which comprises a plurality of sidewalls, a bottom, and a top to define a space for containing wafers, an opening being formed on one sidewall, and a door with an outer surface and an inner surface. The top of the container body is disposed with a robotic flange which comprises a foolproof structure and a hemi-circular snap-hook portion that are disposed at the center and its circumference of a lower surface of the robotic flange facing the top. The foolproof structure has a geometric hole for a protruding portion on the top of the container body to be plugged in. After the protruding portion is plugged into the geometric hole, the robotic flange is further rotated along the container body about 180 degrees for the hemi-circular snap-hook portion to be engaged in a hemi-circular supporting portion on the top of the container body.