A manufacturing method of a plate-shaped object includes a shield tunnel forming step of forming plural shield tunnels in a plate-shaped workpiece formed of a hard material and an etching step of etching the shield tunnels by an etchant. The plate-shaped object is capable of being bent by an external force. In the shield tunnel forming step, plural shield tunnels are formed in a first shield tunnel region having a first length along a line-shaped first processing-planned region set on one surface of the workpiece, and plural shield tunnels are formed in a second shield tunnel region having a second length along a line-shaped second processing-planned region that is different from a region on an extension line of the first processing-planned region and is adjacent to the first processing-planned region on the one surface.