The present invention provides a heavy metal detecting device and the fabricating method thereof. The heavy metal detecting device includes a substrate and a nano-metal-particle array. The fabricating method of the heavy metal detecting device includes following steps of: (S1) preparing a substrate, cleaning the substrate with a first liquid, and drying the substrate with a first gas; (S2) soaking the substrate in a first solution; (S3) after soaking the substrate for a first period of time, cleaning and drying the substrate with the first liquid and the first gas respectively; (S4) soaking the substrate in a pre-synthesized nano-metal-particle solution; and (S5) after soaking the substrate for a second period of time, cleaning and drying the substrate with a second liquid and the first gas respectively. Compared to the prior arts, the heavy metal detecting device of the present invention has the advantages of simplicity and rapidity. |