An LED illuminating device includes an optical section (10), an electrical section (30), and a heat dissipation section (20) arranged between the optical section (10) and the electrical section (30). The heat dissipation section is provided with a heat dissipation device (200) which includes a heat sink (23), a mounting seat (24), and a heat pipe (22) connecting the mounting seat with the heat sink. The heat sink includes a solid base (231) and a plurality of fins (232) extending radially and outwardly from the base. The base is provided with a through hole (233). Alight source (11) is provided in the optical section and attached to the mounting seat. The heat pipe includes an evaporating portion (222) attached to the mounting seat, and a condensing portion (221) fittingly received in the through hole of the base.