To provide an apparatus for supplying a constant quantity of abrasive that can accurately control abrasive quantity supplied to a blasting machine.A rotating disk 20 that rotates in the horizontal direction is provided inside an abrasive tank 10, with a gap 3 being capable to rotate the rotating disk 20, being formed at an end 11a of a mixed fluid flow path 11 arranged on one surface of the rotating disk 20, and at an end 12a of a gas flow path 12 arranged facing other surface of the rotating disk 20 via the rotating disk 20 at the end 11a of the mixed fluid flow path 11. Hole sections 21 are provided in the rotating disk 20 on a rotation locus passing through the gap 3, equally spaced and passing through in a thickness direction of the rotating disk 20, with stirrer blades 22 protruding from the upper surface of the rotating disk 20, and the rotating disk 20 being immersed in abrasive stored inside the abrasive tank 10, except for a part positioned in the gap 3.