A pyrimidinone compound represented by formula (1) has excellent efficacy in controlling harmful arthropods. (In the formula: A represents a nitrogen atom or CR as for A and A A represents a nitrogen atom and A represents CR or A represents CR and A represents a nitrogen atom Q represents an oxygen atom or a sulfur atom G represents e.g. a C2 C10 open chain hydrocarbon group including at least one halogen atom R represents a C1 C6 open chain hydrocarbon group that may include at least one halogen atom R represents e.g. a C1 C6 open chain hydrocarbon group that may include at least one halogen atomR represents e.g. a hydrogen atom R R and R each independently represent e.g. a hydrogen atom n represents 0 1 or 2 and p represents 0 1 2 or 3.)
