A novel O-(N-alkoxy-pyridinecarboximidoyl)-phosphate represented by the following formula: ##STR1## wherein X is a halogen atom, a lower alkyl group, a lower acyloxy group, a trifluoromethyl group or a nitro group; Y is an oxygen atom or a sulfur atom; R is a lower alkyl group; n is an integer of 0 to 3; and Z.sub.1 and Z.sub.2 are each a lower alkoxy group, a lower alkylthio group, a phenyl group which may be substituted by a lower alkyl group, a phenoxy group, a haloalkoxy group or a lower alkylamino group, useful as an active ingredient of insecticides or acaricides.