A server device includes: a communication unit configured to perform communication with at least one refrigerator; memory; and at least one processor, wherein the instructions, when executed by the at least one processor individually or collectively, cause the refrigerator to: receive state information of the at least one refrigerator through the communication unit and store the state information in the memory, calculate a frost formation index value for frost formation or a dew formation index value for dew formation of each of the at least one refrigerator based on the stored state information and store the index value in the memory, and diagnose a frost formation state or a dew formation state of the at least one refrigerator based on index values cumulatively stored during a predetermined period of time.