PROBLEM TO BE SOLVED : To provide an easier mechanism making it possible to detect opening of a housing part for housing an article.SOLUTION : A signal processing device includes : a processor for executing a program; and a memory for storing the program for causing the processor to function as a detection section which sends signals to one or more signal lines formed by a breakable material so as to pass through regions corresponding respectively to one or more housing parts for housing articles, of a package having the one or more housing parts, and detects opening of the respective housing parts on the basis of whether the signals sent to the one or more signal lines are fed back via the respective regions.SELECTED DRAWING : Figure 2COPYRIGHT : (C)2019, JPO&INPIT