A data communication system and a radiation image capturing system are described. According to one implementation, a data communication system includes a wireless terminal an access point and a channel determination section. The channel determination section carries out calculation processing for calculating an influence rate as a score for each of a plurality of channels, and determines a channel having the smallest calculated score to be a channel used, and classifies the influence rate by the interfering radio wave into a plurality of zones, sets the score in each of the zones so that the value of the score is higher as transmission/receiving of the data between the wireless terminal and the access point of the system becomes more difficult when the interfering radio wave having the strength of the zone exists, adds the scores of each zone, and calculates the score.
