In order to improve the finishing efficiency of traditional plane magnetic abrasive finishing (MAF), we have previously proposed an effective plane MAF process combined with an electrolytic process and developed a special compound machining tool for the electrolytic magnetic abrasive finishing (EMAF). In this research, the EMAF process is divided into two finishing steps. The first finishing step is the EMAF step, and a single MAF step constitutes the second finishing step. The machinability of SUS304 material can be improved through the formation of passive films from the electrolytic process in the EMAF step. Meanwhile, the passive films can be rapidly and easily removed by friction between the magnetic particles and the workpiece-generated mechanical machining force. Thus, the surface finishing efficiency can be greatly improved. Compared with a dedicated MAF machining tool or a dedicated electrolytic machining tool, this special compound machining tool can synchronously achieve MAF and electrolytic processes to make the processing more convenient. This study focuses on exploring mechanical finishing characteristics of the special compound machining tool through MAF experiments. Additionally, EMAF experiments are conducted under the optimal mechanical finishing conditions. The experimental results of the EMAF process show that the surface roughness Ra can be reduced to less than 30 nm at the 4-min EMAF step, and it can be further reduced to 20 nm at the 10-min MAF step.