A multi-staged cam assembly comprises a connecting element 1 secured to a tip of a stamping pedal 2; a cam 10 of which a front end is secured to the other end of the element 1, wherein the element 1 is guided along an outer periphery of the cam 10; a drive shaft 6 to which a drum beating rod 5 is fixed; and a revolving body 3 comprising a boss 14 and a space keeping plate 16, wherein a hole 7 for the drive shaft 6 is formed in the boss 14. An elongated hole 17 is formed in the middle of the plate 16. A bolt 22 is inserted in the hole 17 and screwed in a screw hole 21 in the front face of the cam 10, such the cam 10 is fixed at a desired position. A length from the center of the hole 7 of the boss 14 to the back end of the cam 10 is varied in a multi-staged way according to the fixed position of the bolt 22 in the hole 17.