PURPOSE: To convert a ketoxime or an aldoxime into a corresponding amide in a high selectivity and in a high production ratio, by bringing a solution of a ketoxime or an aldoxime into contact with a specific strongly acidic catalyst.

CONSTITUTION: (A) A solution of a ketoxime or an aldoxime in a solvent such as an organic sulfoxide of the formula R1SOR2 (R1 and R2 are each a 1-5C alkyl or a 6-12C aryl) is brought into contact with (B) a heterogeneous strongly acidic catalyst being a carrier with a sulfonated benzene ring (e.g. a benzene ring of the formula {R3 to R7 are each one or several electron-withdrawing groups such as NO2, SO3H, a halogen, etc., and other groups are each H or an (aryl)alkyl and one or more of R3 to R7 are groups -R-P [R is a (substituted) 1-5C alkyl, a (substituted) 6-12C aryl or an arylalkyl] and -P is P and a part of the carrier} to convert the ketoxime or the aldoxime of the component A into a corresponding amide.