A refrigerator comprising: at least one temperature sensor configured to sense a temperature of a refrigerating compartment, a freezing compartment, or out air; a door switch configured to operate when the door is opened or closed; a memory; a selecting unit configured to receive a diagnosis execution command; a sound output unit; a controller configured to generate product information based on at least one of a sensed temperature of the refrigerating compartment, of the freezing compartment, or of the out air or based on an operation of the door switch; start periodically storing product information in the memory at predetermined time periods after powering on the refrigerator at a time TG, wherein the amount of product information that is storable in the memory corresponds to the product information for a set number of predetermined time periods, updating the stored product information after the set number of predetermined time periods after the time TG has passed by storing the current product information instead of the oldest product information in the memory, upon receipt of a diagnosis execution command at a time TS, - generate operation information, -- if the time TS is before the set number of predetermined time periods after time TG has passed, storing the operation information in the memory after the latest product information, -- if the time TS is after the set number of predetermined time periods after the time TG has passed, delete the oldest product information and write the operation information in the memory instead of the oldest product information, to output a signal sound corresponding to product information including the operation information via the sound output unit. at least one temperature sensor configured to sense a temperature of a refrigerating compartment, a freezing compartment, or out air; a door switch configured to operate when the door is opened or closed; a memory; a selecting unit configured to receive a diagnosis execution command; a sound output unit; a controller configured to generate product information based on at least one of a sensed temperature of the refrigerating compartment, of the freezing compartment, or of the out air or based on an operation of the door switch; start periodically storing product information in the memory at predetermined time periods after powering on the refrigerator at a time TG, wherein the amount of product information that is storable in the memory corresponds to the product information for a set number of predetermined time periods, updating the stored product information after the set number of predetermined time periods after the time TG has passed by storing the current product information instead of the oldest product information in the memory, upon receipt of a diagnosis execution command at a time TS, - generate operation information, -- if the time TS is before the set number of predetermined time periods after time TG has passed, storing the operation information in the memory after the latest product information, -- if the time TS is after the set number of predetermined time periods after the time TG has passed, delete the oldest product information and write the operation information in the memory instead of the oldest product information, - generate operation information, -- if the time TS is before the set number of predetermined time periods after time TG has passed, storing the operation information in the memory after the latest product information, -- if the time TS is after the set number of predetermined time periods after the time TG has passed, delete the oldest product information and write the operation information in the memory instead of the oldest product information, -- if the time TS is before the set number of predetermined time periods after time TG has passed, storing the operation information in the memory after the latest product information, -- if the time TS is after the set number of predetermined time periods after the time TG has passed, delete the oldest product information and write the operation information in the memory instead of the oldest product information, to output a signal sound corresponding to product information including the operation information via the sound output unit.