A sterilizing module includes a main body and a light source. The main body includes an inner surface, an outer surface and an internal space to treat a target substance in a fluid and connected an inlet and a outlet. The light source is configured to emit light toward the internal space to sterilize the target substance in the fluid. The light source includes a substrate and a plurality of light emitting structures disposed on the substrate. The plurality of light emitting structures is disposed to be spaced apart each other. A first distance between two light emitting structures is adjacent to each other varies depending on a second distance from each light emitting structure to the inner surface of the main body. The second distance has a maximum value and a minimum value of illuminance and a difference between the maximum and the minimum value thereof is about more than 75%.