Abstract: An improved motion generating mechanism for use in a music box to drive decoration articles associated therewith is disclosed. A crank arm eccentrically attached to the outer side of the driving wheel associated with the playing roller of a music box is circularly moved in synchronism with the driving wheel. At each end of the crank arm is disposed an engagement protrusion respectively. A securing seat is fixed to the mounting plate of the music box and to the base plate of the outer case with a supporting base pivotally associated therewith respectively; each supporting base is provided with a swing arm having an elongated guide groove disposed thereon; in each groove is slidably located the engagement protrusion so that the supporting bases are able to be pivotally moved in synchronism with the crank arm. To each supporting base is secured a mounting pole onto which a decoration article is mounted. Each mounting pole is led through an elongated slot disposed on the top of an upper lid.