Disclosed is a network management apparatus for priority channel assignment to acquire available channels in a frequency sharing band, including: a signal intensity measurer measuring a received signal intensity for an input signal; and a controller verifying usable candidate channels in the same channel and an adjacent channel of a TV band device (TVBD) for each predetermined frequency based on the measured received signal intensity, verifying available channels of the TVBD based on the verified usable candidate channels in the same channel and the adjacent channel, calculating the decreased number of available channels of the TVBD predicted for each channel after channel reassignment, and assigning channels to be reassigned based on the calculated decreased number of available channels of the TVBD.