An LED heat sink and a manufacturing method thereof are disclosed. The LED heat sink includes a main body having a heat receiving section and an extended heat transfer section. The heat transfer section is externally provided with a plurality of receiving grooves for correspondingly connecting with a plurality of radiating fins. The LED heat sink manufacturing method includes the steps of molding a main body using a half-molten metal material and cooling the main body, so that the cooled main body is connected with a plurality of radiating fins to form an integral unit. With the LED heat sink manufacturing method, it is able to manufacture an LED heat sink having a relatively complicated radiating fin structure or being formed of two or more types of materials, and to largely reduce the time, labor and material costs of the LED heat sink.