In Indonesia traditional medicine has become the nation's culture. However, research data and adequate research methodologies for evaluating the effects of traditional medicine are still lacking. Guava leaf are widely used to treat various diseases traditionally, one of them diarrhea. Vibrio cholerae became one of the diarrhea bacteria that the incidence rate is still high in Indonesia. The aim of this research is to know the antibacterial power of guava leaf methanol extract (Psidium guajava Linn) to Vibrio cholerae bacteria and to assess the minimum inhibitory concentration and concentration of minimal bactericidal concentration of guava methanol extract against Vibrio cholerae bacteria. This research was conducted by laboratory experimental method. Antibacterial test was performed by diffusion method and dilution with streak confirmation. The research was conducted in Microbiology Laboratory of POLTEKKES Bandung in May-June 2017 with the extraction of guava leaf at STIH ITB Laboratory. The result of antibacterial test by diffusion method showed the formation of inhibition zone at concentration of 100% extract methanol of guava leaf with an average diameter are 16.02 mm. The result of dilution test showed that KHM in methanol extract of guava leaf at concentration 6,25% and KBM at concentration 12,5%. Active substances such as flavonoid, tannin, and saponin act as an antibacterial agent. This study shows that there is antibacterial power of guava methanol extract (Psidium guajava Linn) against Vibrio cholerae bacteria.Di Indonesia pengobatan tradisional sudah menjadi budaya bangsa. Namun data penelitian serta metodologi penelitian yang memadai untuk mengevaluasi efek obat tradisional masih sangat kurang. Daun jambu biji banyak digunakan untuk mengobati berbagai penyakit secara tradisional, salah satunya diare. Vibrio cholerae menjadi salah satu bakteri penyabab diare yang angka kejadiannya masih tinggi di Indonesia. Penelitian ini bertujuan untuk mengetahui daya antibakteri ekstrak metanol daun jambu biji  (Psidium guajava Linn) terhadap bakteri Vibrio cholerae dan menilai konsentrasi hambat minimal serta konsentrasi bunuh minimal ekstrak metanol daun jambu biji  (Psidium guajava Linn) terhadap bakteri Vibrio cholerae. Penelitian ini dilakukan dengan metode eksperimental laboratorik. Uji antibakteri dilakukan dengan metode difusi dan dilusi dengan konfirmasi streak. Penelitian dilakukan di Laboratorium mikrobiologi POLTEKKES Bandung pada bulan Mei-Juni 2017 dengan ekstraksi daun jambu biji di Laboratorium STIH ITB. Hasil uji antibakteri dengan metode difusi menunjukan terbentuknya zona hambat pada konsentrasi 100% ektrak metanol daun jambu biji dengan diameter rata-rata 16,02 mm. Hasil uji dengan metode dilusi ditemukan KHM pada ekstrak metanol daun jambu biji konsentrasi 6,25% dan KBM pada konsentrasi 12,5%. Zat aktifnya seperti flavonoid, tanin, dan saponin diperkirakan berperan dalam efek antibakteri. Penelitian ini menunjukkan bahwa terdapat daya antibakteri ekstrak metanol daun jambu biji (Psidium guajava Linn) terhadap bakteri Vibrio cholerae.