To obtain the subject compound useful as an intermediate for synthesizing compounds used as the active ingredients of nematicides for controlling plant-injuring nematodes.

A compound of formula I (R is a halogen, nitro: R9 is a 1-30C alkyl, a 3-7C cycloalkyl, a 7-9C aralkyl) except 2-methylthio-5-chlorobenzaldehyde and 2-benzylthio-6-chlorobenzaldehyde. A compound of formula II (R9 is a 1-6C alkyl or benzyl: R7 is a halogen, especially preferably Cl atom), especially 2- benzylthio-3-chlorobenzaldehyde, is preferable in the compound of formula I. The compound of formula I is obtained by reacting a substituted halobenzaldehyde of formula III (R8 is a halogen) with the solution of a thioalcohol of the formula R9SH in the presence of a base. The compound of formula I is reacted with the solution of hydroxylamine-o-sulfonic acid and subsequently cyclized into a compound of formula IV used as an active ingredient for nematicides.