Copper nitride (Cu3N) thin films were deposited at 300 degrees C on glass substrates by reactive magnetron sputtering method with changing various nitrogen flow rates. The results showed that the nitrogen flow rate has a significant effect on the properties of the Cu3N thin films. XRD data exhibited that two phases of Cu3N and Cu coexisted for the thin films deposited at 300 degrees C, irrespective of nitrogen flow rate. The preferential orientation of the film grown at 400 degrees C was transformed from Cu3N to Cu phase. The optical band gap was gradually increased with increasing the nitrogen flow rate. The grain size showed the minimum of 22 nm for the Cu3N thin film deposited at 30%, where the highest value of the carrier concentration was obtained. The results suggest that the properties of the Cu3N thin films can be controlled by the nitrogen flow rate.