The field emission current from ann-type GaN is theoretically calculated as a function of carrier concentrationn.The obtained emission current densityjincreases slowly with increasingneven though the band bending has the oppositendependence. In evaluating thendependence of field emission, the internal voltage drop due to field penetration is found to be crucial. The current densityjis also calculated for several electron affinities χ. It seems that at the lowest χ and at high field,F,the calculated emission currents from the bulk states can be close to the measured values. The electric field at the GaN conical tip is found to be very high in the large area and yield such a large emission current as measured in experiment.