To provide a disk brake for a vehicle in simple construction and can securely prevent frictional pads from abrading eccentrically and furthermore reduce the weight of the frictional pad.

The disk brake oppositely disposes a pair of frictional pads 6, 6 comprising a backing 6b and a lining 6a between an action portion 5a and a reaction portion 5b of a caliper body 5 arranged spanning the outer the periphery of a disk rotor 2 while interposing a disk rotor therebetween. The slide area of the disk rotor 2 of the linings 6a, 6a at braking is formed so that a disk rotation outlet side when starting the vehicle is smaller than a disk rotation inlet side in the action portion side of the lining 6a and the disk rotation inlet side is smaller than the disk rotation outlet side in the reaction portion side of the lining 6a.