To solve problems of conventional erasing devices such as a friction body, which may cause a frictional blur of a non-thermochromism ink in erasing written lines written with both of a non-thermochromism ink and the thermochromism ink, and an ohmic heating device needing a heater temperature controlling device, which can be hardly mounted in a portable apparatus in terms of cost, and incapable of ensuring stable power supply and safety and of finely erasing written lines.

In a thermochromism ink erasing device, heating over the width of the wire diameter is carried out by using a nichrome wire as an ohmic heating body, and power is supplied by electric discharge from a capacitor primarily storing electric charges from a portable battery. When the nichrome wire is heated, a written line written with a thermochromism ink is finely erased by stable overheating for a short time.