A signal processing device comprising: a processor that is configured to execute a program; and a non-transitory computer-readable memory that is configured to store the program for causing the processor to execute a method, the method comprising: transmitting a signal to one or more signal lines (36, 38) 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 one or more respective articles; and detecting seal breakage of each container portion on the basis of whether the transmitted signal returns via each region, wherein the processor is further configured to determine that the transmitted signal returns by checking a status of a general purpose input/output (GPIO) of the processor, and wherein seal breakage of a first container portion is detected in a case in which a first signal does not return via a first region when a predetermined delay time has elapsed since a transmission time of the first signal that is to pass through the first region corresponding to the first container portion, wherein the first signal comprises a pulse signal having a predetermined pulse width, characterized in that the predetermined pulse width being selected such that a fluctuation of the delay time of the first signal is absorbed by the predetermined pulse width and a detection failure of the seal breakage is prevented, and wherein the predetermined pulse width is set in advance via a data input-output unit. a processor that is configured to execute a program; and a non-transitory computer-readable memory that is configured to store the program for causing the processor to execute a method, the method comprising: transmitting a signal to one or more signal lines (36, 38) 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 one or more respective articles; and detecting seal breakage of each container portion on the basis of whether the transmitted signal returns via each region, transmitting a signal to one or more signal lines (36, 38) 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 one or more respective articles; and detecting seal breakage of each container portion on the basis of whether the transmitted signal returns via each region, wherein the processor is further configured to determine that the transmitted signal returns by checking a status of a general purpose input/output (GPIO) of the processor, and wherein seal breakage of a first container portion is detected in a case in which a first signal does not return via a first region when a predetermined delay time has elapsed since a transmission time of the first signal that is to pass through the first region corresponding to the first container portion, wherein the first signal comprises a pulse signal having a predetermined pulse width, characterized in that the predetermined pulse width being selected such that a fluctuation of the delay time of the first signal is absorbed by the predetermined pulse width and a detection failure of the seal breakage is prevented, and wherein the predetermined pulse width is set in advance via a data input-output unit.