A new magnetic deburring method for a drilled hole on the inside of tubing is proposed in this study. This internal deburring method applies the magnetic field assisted machining process by using a magnetic machining jig (permanent magnet tool). In this research, we examined experimentally the deburring of a drilled hole on the inside of SUS304 stainless steel tubing. A processing unit and magnetic machining jig were made, and the processing unit was set on a lathe machine. The deburring experiment was performed for a drill hole 3 mm in diameter. The results showed that the internal burr could be removed using this magnetic deburring process and the height of the burr could be successfully decreased from 163 μm to 1 μm. Thus, it was proved that this magnetic deburring method was effective for the internal deburring of long tubing.