A thermochromic writing instrument contains a thermochromic ink, wherein a writing body 8 is accommodated in a barrel 2 movably in a longitudinal direction, an operation portion 5 is provided on the outer surface of the barrel 2, and a pen tip 81 of the writing body 8 is constituted so as to be projectable/retractable from/into a front-end hole 31 of the barrel 2 by operating the operation portion 5. The thermochromic ink 83 is contained in the inside of the writing body 8, the pen tip 81 capable of ejecting the thermochromic ink 83 is provided at the front end of the writing tool, and a friction portion 4 capable of thermally changing the color of the handwriting of the thermochromic ink 83 by the frictional heat generated when the handwriting is rubbed with the friction portion 4 is provided on the outer surface of the barrel 2.