A photocatalyst lamp is provided. The photocatalyst lamp includes a first printed circuit board, pluralities of first light-emitting diodes and a heat sink. The first light-emitting diodes, which can emit visible light, are disposed on the first printed circuit board, and the first printed circuit board is disposed under the heat sink, which includes pluralities of cooling fins. The present invention is characterized by the fact that the photocatalyst lamp further includes a second printed circuit board, pluralities of second light-emitting diodes and photocatalyst material. The photocatalyst material is coated on the cooling fins, and the second light-emitting diodes, which can emit ultra-violet to catalyze the photocatalyst material, are disposed on the second printed circuit board. The air, therefore, is purified. In addition, the heat sink further includes a fan assembly to increase the efficiency for the photocatalyst lamp to purify the air.
