A color-memorizing photochromic writing instrument, which comprises a writing tip portion connected to a light-shielding tubular member or refill; and a color-memorizing photochromic ink, wherein the ink is prepared by dissolving, dispersing or suspending a diarylethene photochromic compound in a vehicle containing at least a solvent and a binder, wherein the diarylethene photochromic compound is in a coloring state, and a color-memorizing photochromic writing instrument set comprising the writing instrument and a color-changing means.