The present invention provides a chamfering device capable of executing the corner portion of a metallic material or a metallic structure member under economical, efficient and satisfactory working environments. The chamfering device for the metallic material comprises a chamfering oscillation terminal extending at the leading end portion of the oscillating direction of an oscillating device and in the direction perpendicular to the oscillating direction and including a bottom portion having a section of a radius of curvature (R) normal to that extending direction and a groove opened toward leading end side, and that oscillating device for vibrating the oscillation terminal in the axial direction thereof in a frequency of 10 Hz to 50 KHz and in a power of 0.01 to 4 KW.