The present invention provides a novel pyridine derivative having the following general formula and its salt: ##STR1## wherein R is a hydrogen atom, a hydroxyl group, an alkoxy group, an alkoxyalkoxy group, and derivatives;R.sup.1 and R.sup.2 may be the same or different, and are a hydrogen atom, an alkoxy group, a halogen atom, an alkylamino group, a dialkylamino group;Z is a methine group or a nitrogen atom;X.sup.1 is an acylamino group, a cycloalkyl group, a halogen-substituted alkoxy group, an alkenyloxy group, an alkynyloxy group, an alkoxycarbonyl group, an alkylamino group, a dialkylamino group, a phenyl group.The pyridine derivative and its salt of the present invention achieve an excellent herbicidal effect on annual and perennial weeds growing in paddy fields and upland fields at a very small dosage.The pyridine derivative and its salt of the present invention have safety to rice, wheat, cotton and corn, and can be suitably applied as a herbicide to a field where these plants are cultivated.