The present invention provides a tooth brush which has excellent operability inside the oral cavity due to the small thickness of a head part, and is capable of sufficiently securing capability of fixing a bristle bundle with flat wires while suppressing the occurrence of chipping or whitening of the head part even when having a large-diameter bristle bundle having an effect of improving actual massage feeling. This tooth brush (1) employs flat wire-type bristles provided with a resin handle body (1a) including a head part (10), and satisfies the condition that: the thickness of the head part (10) is 2-4 mm inclusive; the fraction of first bristle holes (11a) having diameters of at least 1.8 mm is at least 10%; two or more of the first bristle holes (11a) are aligned in the longitudinal direction of the handle body (1a); and for least one pair of the first bristle holes (11a) adjacent to each other in the longitudinal direction, the ratio of a stress generation parameter P1 to a longitudinal stress mitigating parameter P2is 20-30%.