A pyridazinone compound represented by formula (I) wherein R1 represents a C1-6 alkyl group or a (C1-6 alkyloxy) C1-6 alkyl group, R2 and R3 represent hydrogen or a C1-6 alkyl group, W represents halogen, etc., Z1 represents a C1-6 alkyl group, Z2 represents a C1-6 alkyl group, a C3-8 cycloalkyl group, etc., and n represents 0, 1, 2, 3 or 4, has a weed-controlling effect and an arthropod-controlling effect.
