A relay device that includes a telephone relay unit and a wireless communication relay unit , wherein the telephone relay unit receives call information from a telephone via a network , and after a communication partner designated by the call information has responded, transmits/receives a voice signal to/from the telephone , the wireless communication relay unit , to which a repeater that is a relaying radio is connected, transmits/receives a voice signal to/from a radio via the repeater , the telephone relay unit determines a destination apparatus that is a radio to be called based on the call information received from the telephone , and transfers a voice signal received from the telephone to the wireless communication relay unit , the wireless communication relay unit transfers a voice signal transferred from the telephone relay unit to the destination apparatus, the telephone relay unit includes: a call destination table in which a record including the call information, an address of the destination apparatus, and an apparatus type of the destination apparatus is stored for each of the radios; and a transfer control table in which a record including the apparatus type and a transfer control mode of a voice signal is stored for each of the apparatus types, and the telephone relay unit determines the apparatus type of the destination apparatus by referring to the call destination table , determines the transfer control mode of a voice signal corresponding to the determined apparatus type by referring to the transfer control table, and transfers a voice signal to the wireless communication relay unit using the determined mode. wherein the telephone relay unit receives call information from a telephone via a network , and after a communication partner designated by the call information has responded, transmits/receives a voice signal to/from the telephone , the wireless communication relay unit , to which a repeater that is a relaying radio is connected, transmits/receives a voice signal to/from a radio via the repeater , the telephone relay unit determines a destination apparatus that is a radio to be called based on the call information received from the telephone , and transfers a voice signal received from the telephone to the wireless communication relay unit , the wireless communication relay unit transfers a voice signal transferred from the telephone relay unit to the destination apparatus, the telephone relay unit includes: a call destination table in which a record including the call information, an address of the destination apparatus, and an apparatus type of the destination apparatus is stored for each of the radios; and a transfer control table in which a record including the apparatus type and a transfer control mode of a voice signal is stored for each of the apparatus types, and the telephone relay unit determines the apparatus type of the destination apparatus by referring to the call destination table , determines the transfer control mode of a voice signal corresponding to the determined apparatus type by referring to the transfer control table, and transfers a voice signal to the wireless communication relay unit using the determined mode. a call destination table in which a record including the call information, an address of the destination apparatus, and an apparatus type of the destination apparatus is stored for each of the radios; and a transfer control table in which a record including the apparatus type and a transfer control mode of a voice signal is stored for each of the apparatus types, and the telephone relay unit determines the apparatus type of the destination apparatus by referring to the call destination table , determines the transfer control mode of a voice signal corresponding to the determined apparatus type by referring to the transfer control table, and transfers a voice signal to the wireless communication relay unit using the determined mode. <EOS>