[Object] To be able to detect seal breakage of a container portion for containing an article by a simpler scheme. [Solution] There is provided a signal processing device including : a processor that executes a program; and a memory that stores the program for causing the processor to function as a detection unit that transmits a signal to one or more signal lines formed of a breakable material in such a manner that the signal passes through regions corresponding to one or more respective container portions of a package for containing articles, and detects seal breakage of each container portion on the basis of whether the transmitted signal returns via each region.