A valve body cover of an automatic transmission, may include a cover plate having a hole, an oil level plug having a cap detachably mounted onto the cover plate from the outside of the cover plate and an insertion extended from the cap and selectively inserted into the hole of the cover plate, and rotational pressing members formed in the insertion of the oil level plug and the cover plate respectively to press the cap against the cover plate while the insertion of the oil level plug inserted in the hole is rotated relatively with respect to the cover plate.