A disc brake pad assembly includes a pad and a shim plate. The shim plate includes locking pieces which are bent from a main body portion towards a pressure plate. The locking pieces are brought into abutment with circumferential edge portions of the pressure plate so as to be displaced in a rotating direction of a rotor. Projecting portions are formed at portions of the circumferential edge portion which are brought into abutment with one surface of each of the locking pieces. A circumferential central portion of a part of each of the projecting portions which faces the one surface projects further than both circumferential end portions thereof. The circumferential edge portion and the one surface of each of the locking pieces are spaced apart from each other at portions of the one surface which lie close to both circumferential end portions thereof.