An optical detecting module with waterproofing function can be installed on a housing of a wearable device and includes an optical detecting component, a light source and a packaging structure. The light source is disposed by the optical detecting component, and the packaging structure provides the waterproofing function to the optical detecting component and the light source. The packaging structure includes a main body, a light emitting unit, alight incoming unit and a waterproofing component. The main body covers the optical detecting component and the light source. The light emitting unit and the light incoming unit are disposed on the main body and respectively face the light source and the optical detecting component. The waterproofing component is filled into a gap formed between the main body and the housing, to prevent moisture from leaking into the gap to rust terminals of the optical detecting component and the light source.