To provide a method for producing a lactam compound, which does not form ammonium sulfate as a by-product, in carrying out a Beckmann rearrangement reaction of a cycloalkanone oxime compound.

It has been found by the present inventors that a Beckmann rearrangement reaction of a cycloalkanone oxime compound proceeds in the presence of a sulfamide compound, to give a corresponding lactam compound. The method for producing a lactam compound comprises carrying out a Beckmann rearrangement reaction of a cycloalkanone oxime compound in the presence of a sulfamide compound, to give a corresponding lactam compound.