PROBLEM TO BE SOLVED: To enable a simple influenza epidemic warning display to be performed by using a humidity sensor which detects relative humidity without making a major change to a configuration of a conventional CPU.SOLUTION: Recognizing absolute humidity of 7 g/mor less as a warning region where an outbreak of influenza virus occurs, relative humidity corresponding to the absolute humidity of 7 g/mor less is read by using a wet air diagram. Also, a correlation formula is created from the read relative humidity by executing a regression analysis between a dry bulb temperature and the relative humidity at a temperature of 21°C or less. Then, measured values of the dry bulb temperature as well as the relative humidity under a usage environment are detected with a temperature sensor as well as a humidity sensor (S1). A CPU: processes data on the detected dry bulb temperature as well as the relative humidity by substituting the same into the correlation formula (S2); determines whether or not a calculation result a is 7 g/mor less (S3); and, when the calculation result a is 7 g/mor less (S3, YES), makes a display section perform a warning display (S4).