Fungicidal activity against phytopathogenic fungi of diarylthiazole compound of N-[4-(4-fluoro) phenyl-2-(N-methyl)piperidin-4-yl-thiazol-5-yl]pyrimidin-2-yl-N-(3-hydroxy-methyl)phenylamine (I) have been determined to be a superior and compound I was used as the leading compounds in this study. Furthermore, the synthesis of this compound was conducted by reacting them with four functional groups, N-cyclopropyl, N-cyclopentyl, N-cyclohexyl, and N-isopropylamine instead of the phenylamine. Also, 2-aminothiazole, 2-(N-ethoxycarbonyl)piperidin-4-yl, and 2-piperidin-4-ylthiazole were introduced as the leads instead of the 2-aminothiazole group of compound I. From this scheme, VIII-1~VIII-4 and XII-1~XIV-4 compounds were newly synthesized and their structures were confirmed by $^1H$-NMR-spectrum. The fungicidal activities of all the synthesized compounds against Phytophthora capsici were examined using the whole plant method. While the $EC_{50}$ value of the commercial fungicide dimethomorph and I was 4.26 mM and that of N-[4-(4-fluoro)phenyl-2-(N-methyl)piperidin-4-yl-thiazol-5-yl]pyrimidin-2-yl-cyclopropylamine (XIV-2) on P. capsici was 0.84 mM. Among the XII-1~XIV-4 chemicals, XIV-2 showed the most potential antifungal activity in vivo. Therefore, XIV-2 can be considered as a viable candidate for the control of phytopathogenic diseases characterized by P. capsici infection, and further studies will be conducted on the mode of action XIV-2.