A pyrimidinone compound represented by formula (1):wherein: A1 represents a nitrogen atom or a CR4； A2 represents a nitrogen atom and A3 represents a CR3b, or A2 represents a CR3a and A3 represents a nitrogen atom； Q represents an oxygen atom or a sulfur atom； G represents a C2-C10 chain hydrocarbon group having one or more halogen atoms, etc.； R1 represents a C1-C6 chain hydrocarbon group optionally having one or more halogen atoms； R2 represents a C1-C6 chain hydrocarbon group optionally having one or more halogen atoms, etc.； R4 represents a hydrogen atom, etc.； R3, R3a, and R3b represent independently of each other a hydrogen atom, etc.； n represents 0, 1, or 2； and p represents 0, 1, 2, or 3 has an excellent efficacy for controlling harmful arthropods.
