It is a purpose of the invention to provide a fault detection system, etc., having improved fault coverage with a reduced number of test patterns to be input to a logic circuit. The fault detection system detects a fault in a logic circuit based on multiple output logic values of the logic circuit after a test input pattern is input. The output logic values are input to the logic circuit as an updated test input pattern. The system comprises: a first acquisition unit which acquires a part of or all of the output logic values; a comparison unit which compares the logic values acquired by the first acquisition unit with those predicted for when there are no faults, or for when there is a specific fault; and a fault judgment unit which judges whether or not there is a fault based on the comparison result obtained by the comparison unit.