To uniformize a wear amount of a brake pad facing a groove formed on a slide plate to extend the life of the brake pad, and to uniformize the contact pressure between slide parts of a brake disc rotor and the brake pad to prevent occurrence of brake squeak.

On a sliding surface of a slide plate, a plurality of curved grooves 3 are formed in a rotating direction of the slide plate, and the groove 3 is formed so that a product of a cosine of an angle formed by a tangent line of one point of the groove 3 with a line drawn from the center in the rotating direction of the slide plate toward the one point on the groove 3, and a square of a distance between the one point on the groove 3 and the center in the rotating direction of both slide plates is set nearly constant at any point on the groove 3.