To provide a manufacturing method for an optical part or its mold, obtaining uniform machined surface in short-time machining.

According to this manufacturing method for an optical part or its mold, a tool is rotated round its axis with the cutting edge directed to the outside, a machining object surface of a workpiece is cut by one portion of a circle drawn by the cutting edge, and simultaneously the tool and the workpiece are relatively linearly moved at a predetermined feed rate in the line direction to perform cutting for one line. Subsequently, the tool and the workpiece are relatively moved in the pitch direction intersecting the line direction only by pick feed amount to perform cutting for the next one line. The rotating speed of the tool is set to 10,000 (rotation/min), and the movement in the line direction is reversed line by line to perform cutting in reciprocation.