Boron contents analyzed by prompt gamma-ray analysis for 19 sedimentary rocks from Late Cretaceous Shimanto belt and Miocene Kumano Formation in the Outer Zone of southwest Japan are reported. Samples were obtained from Uwajima region close to the Uwajima granodiorite body in southwest Shikoku and Kumano region close to the Kumano Acidic Rocks in southeastern Kii peninsula. Boron contents of sandstone and shale range 13-113 ppm and 19-302 ppm, respectively. Most of samples show negative correlation between SiO2 and boron contents reflecting the mode of clay minerals in the samples. Three shalesamples from Uwajima region show rather high boron content (＞240 ppm). Boron content of these samples might be affected by contact metamorphism of Uwajima granodiorite body which includes tourmaline rich lithologies.