PURPOSE: To provide an oil quantity regulator having an inlet valve closing mechanism which is easily manufactured and has high float sucking force.

CONSTITUTION: An oil quantity regulator comprises an inlet valve closing mechanism 1 having a magnet which vertically moves the valve disc 33d of an inlet valve 33 according to the vertical movements of a float 34 mounted at a float mounting fitment 41 to hold an oil level constant and attracts the float 34 in a vertical direction when the oil level is abnormally raised to forcibly move the disc in its closing direction. The mechanism 1 has one magnet 5, two iron pieces 6A, 6B for sandwiching the magnet 5, a holding member 4 movably engaged with the magnet 5 and the pieces 6A, 6B for sandwiching to attract the magnet 5, and a cover member 15 for limiting the movements of the magnet 5 and the pieces 6A, 6B in the member 4.