A thermochromic writing instrument contains a thermochromic ink, wherein a writing body is accommodated in a barrel movably in a longitudinal direction, an operation portion is provided on the outer surface of the barrel, a pen tip of the writing body is constituted so as to be projectable/retractable from/into a front-end hole of the barrel by operating the operation portion, the thermochromic ink is contained in the inside of the writing body, the pen tip capable of ejecting the thermochromic ink is provided at the front end of the writing tool, and a friction portion capable of thermally changing the color of the handwriting of the thermochromic ink by the frictional heat generated when the handwriting is rubbed with the friction portion is provided on the outer surface of the barrel.