A management device includes an obtaining unit that obtains the attribute data of at least a communication performed among terminal devices in a communication system; a determining unit that performs a predetermined determination operation based on the attribute data obtained by the obtaining unit, and outputs the likelihood of the communication being followed by other communication relevant to the communication; and a communication control unit that, based on the output of the determining unit, controls the period of time during which the terminal devices involved in the communication are able to use the line of the communication system on a priority basis.