To obtain a thermally color-changing fiber sheet that lower the brightness of color at the parts where hollow particles are broken by heating at least a part of a colored fibrous sheet carrying thermoplastic resin hollow particles to break the hollow particles at the parts.

100 pts.wt. of polyester fiber nonwoven fabric sheet colored by coloring dye and/or coloring pigment, as blend-colored polyester fiber nonwoven sheet are treated with 10-50 pts.wt. of hollow particles that has an outer diameter of 0.2-2 μm and shell thickness of 0.05-0.3 μm and a porosity of more than 15 %, is made of a thermoplastic resin melting lower than the above-stated polyester as a styrene-acrylic copolymer and has the hollow part filled with a color less gas as air and 5-50 pts.wt. of a binder emulsion as a polyurethane resin and they are dried to prepare thermally color-changing fiber sheet 1. At least a part of the resultant sheet is heated at a temperature higher than the melting point of the resin constituting the hollow particles but lower than the melting point of the polyester constituting the sheet to break the hollow structure of the hollow particles 3 on the heated part, thereby changing the color.