Improved processes for producing an -caprolactam using a solid catalyst and for producing a catalyst which can be used in the production of -caprolactam are provided. In the present invention, a solid catalyst such as a zeolite is treated with an aqueous solution containing an ammonia and at least one compound selected from the group consisting of quaternary ammonium compounds and lower alkylamines. In accordance with the present invention, a zeolite having a high catalyst activity and a long lifetime is produced, and a solid catalyst which has been used in the production of -caprolactam can be re-activated. In the present invention, by using the thus obtained zeolite and/or the thus activated solid catalyst, an -caprolactam is produced in a high yield over the long period of time.