A communication system and a receiving device that ensure reducing a risk of performing pairing processing on an incorrect pair caused by presence of a large count of communication candidates are provided. The communication system 1 includes an extractor 55 to extract the communication candidates among a plurality of biological information measuring devices 10 by the receiving device 50. The extractor 55 compares radio field intensities of a plurality of pairing signals with a second threshold value larger than a first threshold value. The first threshold value specifies a lower limit of the radio field intensity at which a transmission of biological information is effectively achieved. The extractor 55 extracts the at least one biological information measuring device 10 transmitting the pairing signal at the radio field intensity exceeding the second threshold value as the communication candidate for this receiving device 50. According to an input operation by an operator, a selector 56 selects the one biological information measuring device 10 as a communication target among the communication candidates extracted by the extractor 55.
