The machining method uses a tool to machine a workpiece set in a jig, the workpiece has a plate-like web part arc-shaped in plan view and a flange part bent and arranged vertically from an edge along the arc shape, the tool has an end cutting edge and a peripheral cutting edge, and the jig has a surface where the web part is placed and a contacting surface where the flange part comes into surface contact. The machining method includes: pressing the flange part against the contacting surface; cutting the flange part by the peripheral cutting edge by feeding the tool in an arc direction of the arc shape; and cutting the web part by the end cutting edge by feeding the tool in the arc direction.