The influence of the nitrogen doping in GaMnAs on the magnetic properties was investigated. The GaMnNAs film was grown by molecular beam epitaxy with a nitrogen plasma source. The GaMnNAs film with a large amount of nitrogen showed super-paramagnetic behaviour. The Arrott-plot and the Curie-Weiss plot also support the paramagnetism. The high concentration of nitrogen caused suppression of the ferromagnetism. One of the possibilities of the suppression is due to the band gap bowing effect, which causes the anti-bonding state of 3d-Mn to locate in the valence band in high nitrogen concentration. (c) 2006 Elsevier B.V. All rights reserved.