A diaminotrifluoromethylpyridine derivative of the formula (I) or its salt: ##STR1## wherein X is --CW.sup.1 R.sup.1, --COCOR.sup.2, --CW.sup.1 NHCOR.sup.2, --C(.dbd.W.sup.1 (W.sup.2 W.sup.3 or --CW.sup.1 N(R.sup.4)R.sup.5, and Y is alkyl, --CW.sup.3 R.sup.6, --COCOR.sup.7, --NHCOR.sup.7, --C(.dbd.W.sup.3)W.sup.4 R.sup.8, --(NH).sub.m SO.sub.2 R.sup.9, --(NH).sub.m SO.sub.2 OR.sup.10 or --(NH).sub.m SO.sub.2 N R.sup.11)R.sup.12, wherein each of R.sup.1, R.sup.6 and R.sup.9, which are independent from one another, is a chain hydrocarbon group which may be substituted, a monocyclic hydrocarbon group which may be substituted, a polycyclic hydrocarbon group which may be substituted, a monocyclic heterocycle group which may be substituted or a polycyclic heterocycle group which may be substituted, each of R.sup.2 and R.sup.7, which are independent from each other, is alkyl which may be substituted, alkoxy which may be substituted, phenyl which may be substituted or phenoxy which may be substituted, each of R.sup.3, R.sup.8 and R.sup.10, which are independent from one another, is alkyl which may be substituted, alkenyl which may be substituted, alkynyl which may be substituted, cycloalkyl which may be substituted, phenyl which may be substituted or benzyl which may be substituted, each of R.sup.4, R.sup.5, R.sup.11 and R.sup.12, which are independent from one another, is alkyl which may be substituted, each of W.sup.1, W.sup.2, W.sup.3 and W.sup.4, which are independent from one another, is an oxygen atom or a sulfur atom, and m is 0 or 1, provided that a combination wherein one of X and Y is --COCF.sub.2 X.sup.1 wherein X.sup.1 is a hydrogen atom, a halogen atom, alkyl or haloalkyl, and the other is --COCF.sub.2 X.sup.2 wherein X.sub.2 is a hydrogen atom, a halogen atom, alkyl, haloalkyl or alkylcarbonyl, or --COOX.sup.3 wherein X.sup.3 is alkyl which may be substituted or phenyl which may be substituted, is excluded.