A thiadiazole compound of the formula (A): ##STR00001## wherein R.sup.1 represents methyl, C3-C7 alkenyl, C2-C7 alkoxyalkyl, C2-C7 alkylthioalkyl, C4-C7 alkoxyalkoxyalkyl, C4-C7 alkylthioalkoxyalkyl, phenyl C1-C2 alkyl in which phenyl may be substituted, phenyloxy C1-C2 alkyl in which phenyloxy may be substituted, phenyl C2-C3 alkoxyalkyl in which phenyl may be substituted, or the substituent of the formula (B): ##STR00002## wherein R.sup.3 represents C1-C3 alkyl, and R.sup.4 represents a hydrogen atom, methyl, ethyl or phenyl which may be substituted; and R.sup.2 represents phenyl C1-C4 alkyl in which phenyl may be substituted, pyridyl C1-C4 alkyl in which pyridyl may be substituted, or pyrimidyl C1-C4 alkyl in which pyrimidyl may be substituted; has an excellent arthropod pests controlling activity.