A heat radiating member mounting structure for enabling multiple heat radiating members to be fastened together in a stack without tools is disclosed. Each heat radiating member has convex portions and lugs formed on each of two upright side flanges at two sides of a flat base thereof such that multiple heat radiating members can be fastened together by means of engaging protruding portions of the lugs of one heat radiating member into locating grooves in the convex portions of another heat radiating member.