an instruction fetch control system prefetches a branch instruction in a pipeline system and fetches a branch target instruction of the branch instruction . the control system comprises a first branch judgement circuit for conducting a branch condition judgement in a stage prior to the branch judgement stage in which a second and original branch judgement of the branch instruction is conducted , and a circuit for starting a prefetch of instructions following said branch target instruction without waiting for the branch judgement stage where the first branch judgement circuit judges that the branch is successful .