A programmable logic controller system comprising: a programmable logic controller device; at least one expansion unit (10b-1, 10b-2); and a connecting bus line (SB', PB') that connects said programmable logic controller device with said at least one expansion unit (10b-1, 10b-2); wherein said programmable logic controller device comprises: a programmable logic controller main body having a CPU unit and one or more I/O units connected by a bus line (SB, PB); and a power unit for supplying power to said programmable logic controller main body, wherein said power unit has status data generating means for generating status data related to said power unit; wherein said CPU unit has a memory with a user access area (A5, A6) which is accessible by a user program stored in a user program memory area of the memory, the user access area having dedicated areas assigned individually to said at least one expansion unit (10b-1, 10b-2) and said programmable logic controller device; wherein said at least one expansion unit (10b-1, 10b-2) comprises: one or more expansion I/O units connected through a bus line (SB, PB); an expansion power unit for supplying power to said one or more expansion I/O units, said expansion power unit including additional status data generating means for generating status data related to said expansion power unit; wherein said programmable logic controller system further comprises a data transmission path between said CPU unit and said power unit and between said CPU unit and the expansion power unit for transmitting status data generated by said status data generating means and the additional status data generating means to said user access area; and said user program includes either an instruction for execution of a specified calculation by using status data transmitted to said user access area as calculation parameter, or an instruction that is a dedicated command for carrying out a specified calculation by using status data transmitted to said user access area as calculation parameter. a programmable logic controller device; at least one expansion unit (10b-1, 10b-2); and a connecting bus line (SB', PB') that connects said programmable logic controller device with said at least one expansion unit (10b-1, 10b-2); a programmable logic controller main body having a CPU unit and one or more I/O units connected by a bus line (SB, PB); and a power unit for supplying power to said programmable logic controller main body, wherein said power unit has status data generating means for generating status data related to said power unit; wherein said CPU unit has a memory with a user access area (A5, A6) which is accessible by a user program stored in a user program memory area of the memory, the user access area having dedicated areas assigned individually to said at least one expansion unit (10b-1, 10b-2) and said programmable logic controller device; wherein said at least one expansion unit (10b-1, 10b-2) comprises: one or more expansion I/O units connected through a bus line (SB, PB); an expansion power unit for supplying power to said one or more expansion I/O units, said expansion power unit including additional status data generating means for generating status data related to said expansion power unit; wherein said programmable logic controller system further comprises a data transmission path between said CPU unit and said power unit and between said CPU unit and the expansion power unit for transmitting status data generated by said status data generating means and the additional status data generating means to said user access area; and said user program includes either an instruction for execution of a specified calculation by using status data transmitted to said user access area as calculation parameter, or an instruction that is a dedicated command for carrying out a specified calculation by using status data transmitted to said user access area as calculation parameter. one or more expansion I/O units connected through a bus line (SB, PB); an expansion power unit for supplying power to said one or more expansion I/O units, said expansion power unit including additional status data generating means for generating status data related to said expansion power unit; wherein said programmable logic controller system further comprises a data transmission path between said CPU unit and said power unit and between said CPU unit and the expansion power unit for transmitting status data generated by said status data generating means and the additional status data generating means to said user access area; and said user program includes either an instruction for execution of a specified calculation by using status data transmitted to said user access area as calculation parameter, or an instruction that is a dedicated command for carrying out a specified calculation by using status data transmitted to said user access area as calculation parameter.