Abstract: A tool assembly apparatus may comprise a sleeve, a locating ball, an elastic locating piece, and a connecting rod. The sleeve has a first end and a second end, and the first end and the second end of the sleeve respectively have an axial first engaging hole and an axial second engaging hole which are communicated to axially penetrate through the sleeve. The inner diameter of the second engaging hole is smaller than the first engaging hole, and the sleeve has a radial through hole penetrating through an outer periphery thereof to communicate with the second engaging hole. The elastic locating piece has a ring body which comprises a locating hole and a cutting portion thereon. The connecting rod comprises a bearing section and a driving section, and a middle section is connected therebetween. The driving section has a locating recess formed thereon.