The aim of the present study was to develop a strain-specific polymerase chain reaction (PCR) primer set for the detection of Bifidobacterium bifidum OLB6378 (OLB6378) that can serve as suitable probiotics for infants. The random amplified polymorphic DNA (RAPD)-PCR technique was used to obtain OLB6378-specific PCR products. One OLB6378-specific RAPD-PCR product was obtained after testing 97 RAPD primers, and was sequenced. Thirteen PCR primer sets were designed from the sequence. One PCR primer set was found to amplify one PCR product when genomic DNA of OLB6378 was used as template. The primer set did not amplify any PCR product when the other genomic DNA was used as template. The primer set was tested with 47 strains of B. bifidum and 20 strains of the other Bifidobacterium species. As a result, we developed an OLB6378-specific primer set, one that should be useful not only for the detection of OLB6378 but also for the quantification of OLB6378.