To provide a toothbrush capable of surely reporting its replacement period by simple constitution in order to prevent polytrimethylene terephthalate (PTT) bristles from being worn, frayed or broken before the replacement period comes, in the toothbrush using the PTT bristles.

In the toothbrush using the PTT bristles 1, a brush 2 composed of one, two or more resins selected from a polyamide resin, a polyethylene terephthalate resin, polybutylene terephthalate resin, polypropylene resin and polyethylene resin is implanted on a part of an implanted surface of a head part as indicator bristles for displaying the changing period of the toothbrush. Also, of the cross sectional area total sum of the entire brushes, the cross sectional area total sum of the PTT bristles is set to 95-60%. The limiting viscosity of the PTT bristles is 0.9-1.3dl/g, and further, the limiting viscosity of the PTT bristles is set to 1.0-1.2dl/g and a boiling water shrinkage rate is set to be ≤0.4%.