A malfunction detection system is provided that can continue or terminate processing appropriately even if a malfunction occurs in an information processing unit. In this regard, the information processing unit receives branch direction information, carries out a conditional branch depending on the branch direction information, and performs an applicable operation on data I. At this time, the information processing unit performs an applicable operation on data J, other than the operated data I, in the conditional branch path and outputs the result for examination, thereby enabling validation of the conditional branch.