A lighting device includes a light source module and a housing mated to a heat sink and covered by a cover. The housing has a first shell portion encircled by an inner sidewall of the heat sink. Alternatively, the housing may further has a second shell portion arranged between the first shell portion and the inner sidewall of the heat sink. The respective ends of the first and second shell portions are covered by a first plate portion and a connecting portion. A cavity is defined by the first shell portion and the first plate portion for accommodating the light source module. A plurality of first thru-holes, second thru holes, third thru holes, fourth thru-holes, and fifth thru holes are formed on the circuit board, the connecting portion, the cover, the first shell portion, and the first plate portion, respectively.