To easily and effectively recognize directivity without impairing flatness of a plate-like optical object.

The protective sheet 1A comprises a base material sheet 2 having light transmission properties, an adhesive layer 3 constituted by re- releasable adhesive, and a display layer 4A inserted therebetween. The layer 4A, for example, has a display function for indicating directivity of a plate-like optical object like a polarizing plate adhered with the sheet 1A. The layer 4A constituted by printing ink is embedded in the layer 3.