A method of producing ε-caprolactam through adipamide as an intermediate, the method comprising a lactamization step of reacting adipamide, formed from a material compound, with hydrogen and ammonia in the presence of a catalyst and a solvent, wherein the catalyst comprises: a metal oxide mainly containing an oxide(s) of one or more metallic elements selected from the group consisting of vanadium, niobium, tantalum, manganese, iron, cobalt, nickel, zinc, gallium, indium, thorium, germanium, tin, and lead, wherein mainly containing the oxide(s) of the one or more metallic element(s) means a state where the chemical properties of the oxide(s) of the one or more metallic element(s) are reflected in the chemical surface properties of the metal oxide; and a metal and/or a metal compound having a hydrogenation ability; and wherein the material compound is a carboxylic acid represented by the following General Formula (I) or (II): [wherein in Formula (I) and Formula (II), R 1 , R 2 , and R 3 each independently represent a hydrogen atom (H) or an alkyl group having 1 to 6 carbon atoms; in Formula (I), X represents -CH 2 -CH 2 -CH 2 -CH 2 -, -CH 2 -CH 2 -CH=CH-, -CH 2 -CH=CH-CH 2 -, -CH=CH-CH=CH-, -CH2-CH 2 -CH 2 -CH(OH)-, -CH 2 -CH 2 -C(OH)H-CH 2 -, -CH=CH-C(OH)H-CH 2 -, -C(OH)H-CH 2 -CH=CH-, or -CH 2 -CH=CH-CH(OH)-; and, in Formula (II), Y represents -CH 2 -CH 2 - or - CH=CH-], or a salt or an ester thereof, or a mixture thereof. wherein the catalyst comprises: a metal oxide mainly containing an oxide(s) of one or more metallic elements selected from the group consisting of vanadium, niobium, tantalum, manganese, iron, cobalt, nickel, zinc, gallium, indium, thorium, germanium, tin, and lead, wherein mainly containing the oxide(s) of the one or more metallic element(s) means a state where the chemical properties of the oxide(s) of the one or more metallic element(s) are reflected in the chemical surface properties of the metal oxide; and a metal and/or a metal compound having a hydrogenation ability; and a metal oxide mainly containing an oxide(s) of one or more metallic elements selected from the group consisting of vanadium, niobium, tantalum, manganese, iron, cobalt, nickel, zinc, gallium, indium, thorium, germanium, tin, and lead, wherein mainly containing the oxide(s) of the one or more metallic element(s) means a state where the chemical properties of the oxide(s) of the one or more metallic element(s) are reflected in the chemical surface properties of the metal oxide; and a metal and/or a metal compound having a hydrogenation ability; and wherein the material compound is a carboxylic acid represented by the following General Formula (I) or (II): [wherein in Formula (I) and Formula (II), R 1 , R 2 , and R 3 each independently represent a hydrogen atom (H) or an alkyl group having 1 to 6 carbon atoms; in Formula (I), X represents -CH 2 -CH 2 -CH 2 -CH 2 -, -CH 2 -CH 2 -CH=CH-, -CH 2 -CH=CH-CH 2 -, -CH=CH-CH=CH-, -CH2-CH 2 -CH 2 -CH(OH)-, -CH 2 -CH 2 -C(OH)H-CH 2 -, -CH=CH-C(OH)H-CH 2 -, -C(OH)H-CH 2 -CH=CH-, or -CH 2 -CH=CH-CH(OH)-; and, in Formula (II), Y represents -CH 2 -CH 2 - or - CH=CH-], or a salt or an ester thereof, or a mixture thereof. <EOS>