Processing method for resin substrate in which the protrusions of the periphery of the resin substrate do not become an obstacle when the resin substrate is divided into individual chips

Provided is a processing method for a resin substrate, in which the protrusions of the periphery of the resin substrate do not become an obstacle when the resin substrate is divided into individual chips. The method includes the following steps: a holding step that holds a resin substrate 20 on a chuck table 10a; a protrusion flattening step in which a cutting blade 83 is positioned at the periphery 22 of the resin substrate 20 for cutting the protrusions 23a~23d to a height aligned with and approximately the same as the height of the central flat portion 21; and a dividing step that operates an X-axis feeding means and a Y-axis feeding means to divide the resin substrate 20 into individual chips 24.