A single-motor massager has a base, a carriage, a gear shaft assembly, a massager assembly and a motor. The base has two gear racks. The carriage is mounted movably on the base. The gear shaft assembly is mounted on the carriage and is mounted movably on the gear racks of the base. The massaging assembly is mounted on the carriage and connects to the gear shaft assembly. The motor drives the massaging assembly of the massager assembly to provide massaging function and to move the carriage and the gear shaft assembly and the massaging assembly along the base. With the two gear racks, the massaging assembly moves stably. With only one motor and the simplified gear shaft assembly and massager assembly, the manufacturing process of the massager is simplified and the cost of the massager is reduced.