A method for detecting errors of a first field-programmable gate array (FPGA) program includes: receiving, by a monitoring program executed on a processor connected to an FPGA on which the first FPGA program is executed, a signal value read out from the first FPGA program; and comparing, by the monitoring program executed on the processor, the signal value to a reference value from a source other than the first FPGA program in order to detect errors of the first FPGA program.