A communication system includes a plurality of communication relay apparatuses relaying communication between the plurality of devices provided inside a LAN and an external server provided outside the LAN. A first communication relay apparatus performs a device search process of searching the LAN for a device, acquires information on a first management target device which is a device whose communication relay process is managed by a second communication relay apparatus, and determines a second management target device which is a device whose communication relay process is managed by the first communication relay apparatus. The first communication relay apparatus determines the second management target device after removing at least partial duplication of the second management target device and the first management target device, by excluding at least some of the first management target device from two or more devices which are retrieved in the device search process.