A programmable controller is of a building block type provided with a plurality of modules including a power supply module and a CPU module. The CPU module includes a microprocessor having a determination control function for determining the adaptability of a power supply capacity of the power supply module by comparing the power supply capacity of the power supply module with a sum total value of current consumptions of the respective modules other than the power supply module. The power supply module supplies a first power used for the determination of the adaptability of the power supply capacity of the power supply module including power supplied to the microprocessor and a second power used for others as at least two independent power supply systems.