An evaluation system (1) includes process execution means (154) for executing a safety program (10), setting means (156) for receiving an evaluation condition including: an input signal to be evaluated; an output signal to be evaluated; and an expected output value, first determination means (156, 154, 158) for changing the value of the input signal, from an initial first input value to a second input value, and determining whether a first output value of the output signal which is determined by the process execution means (156, 154, 158) is identical to the expected output value, second determination means (156, 154, 158) for restoring the value of the input signal, from the second input value to the first input value, and determining whether a second output value of the output signal is identical to the first output value, and output means (160) for outputting a determination result.