To provide a whiteboard eraser which can completely erase letters written on a whiteboard by a marker, by impregnating the surface of the whiteboard to be erased with a nonvolatile release agent of silicon series.

Raised fibers 2 are fitted to one longitudinally long surface of a sponge material 1 shaped like a square pillar. These raised fibers 2 are impregnated with the nonvolatile release agent 3 of silicon series and a cover 4 is so provided as to cover three other longitudinally long surfaces of the sponge material 1.