Abstract: An improved commutator heat dissipating device for alternators, the commutator including a heat dissipating plate, a base plate, a top cover, terminals, and diodes. The heat dissipating plate has a body including a plurality of recesses for receiving the diodes, and a plurality of integrally connected wavy cooling fins on an opposite side thereof. An insulation plate is disposed between a bottom side of the body and the base plate. Securing posts pass through through holes in the heat dissipating plate to secure the heat dissipating plate and the base plate. The terminals include insulating elements and conductive plates. The insulating elements are capable of positioning the terminals by means of limiting blocks and posts of the heat dissipating plate to enable the conductive plates to be soldered with the diodes. The commutator has excellent heat dissipating effects and enhanced structural strength to achieve smooth operation of machine elements.