The present invention provides an LED lamp heat sink which has excellent thermal conductivity and moldability, is light in weight, and can be produced at low cost. The LED lamp heat sink is partially or wholly made of a thermally conductive resin composition and cools an LED module. The thermally conductive resin composition contains at least: 10 to 50 wt. % of thermoplastic polyester resin (A) having a number average molecular weight of 12,000 to 70,000; 10 to 50 wt. % of polyester-polyether copolymer (B); and 40 to 70 wt. % of scale-like graphite (C) having a fixed carbon content of 98 wt. % or more and an aspect ratio of 21 or more. Specific gravity of the thermally conductive resin composition is 1.7 to 2.0. Heat conductivity of the thermally conductive resin composition in a surface direction is 15 W/(m·K) or more.