A disc brake device for a vehicle, the disc brake device comprising: a brake disc; a pair of friction pads (P, P') facing each other with the brake disc sandwiched therebetween; a brake caliper that has a pair of arm sections (Ca, Ca') disposed on the back sides of the friction pads (P, P') and is slidably supported by a fixed bracket; a piston that is slidably fitted into a cylinder hole (Ch) provided in one of the arm sections (Ca) of the brake caliper and is capable of pressing one of the friction pads; a shim plate that is attached to the back plate of the one of the friction pads and is present between the back plate and the piston; and pressing means capable of giving a pressing force to the piston, wherein the pressing means is capable of giving a pressing force to the piston while applying a rotational force to the piston, wherein the back plate facing the piston with the shim plate sandwiched therebetween is provided with a plurality of protrusions (t2, t2') protruding toward the piston, the protrusions (t2, t2') being spaced apart from each other, and the shim plate is provided with a plurality of engaging holes (h2, h2') into which the plurality of protrusions (t2, t2') is fitted to prevent the shim plate from being co-rotated with the piston by the rotational force, wherein rotation limitation means to restrict rotation of the piston in the cylinder hole (Ch) is provided between the piston and the back plate; and characterised in that the rotation limitation means comprises a first protrusion protruding toward the piston and integrally provided in the back plate, and at least one engaging groove provided in a front end wall of the piston, wherein the first protrusion is configured to fit into the at least one engaging groove to restrict rotation of the piston in the cylinder hole (Ch). a brake disc; a pair of friction pads (P, P') facing each other with the brake disc sandwiched therebetween; a brake caliper that has a pair of arm sections (Ca, Ca') disposed on the back sides of the friction pads (P, P') and is slidably supported by a fixed bracket; a piston that is slidably fitted into a cylinder hole (Ch) provided in one of the arm sections (Ca) of the brake caliper and is capable of pressing one of the friction pads; a shim plate that is attached to the back plate of the one of the friction pads and is present between the back plate and the piston; and pressing means capable of giving a pressing force to the piston, wherein the pressing means is capable of giving a pressing force to the piston while applying a rotational force to the piston, wherein the back plate facing the piston with the shim plate sandwiched therebetween is provided with a plurality of protrusions (t2, t2') protruding toward the piston, the protrusions (t2, t2') being spaced apart from each other, and the shim plate is provided with a plurality of engaging holes (h2, h2') into which the plurality of protrusions (t2, t2') is fitted to prevent the shim plate from being co-rotated with the piston by the rotational force, wherein rotation limitation means to restrict rotation of the piston in the cylinder hole (Ch) is provided between the piston and the back plate; and characterised in that the rotation limitation means comprises a first protrusion protruding toward the piston and integrally provided in the back plate, and at least one engaging groove provided in a front end wall of the piston, wherein the first protrusion is configured to fit into the at least one engaging groove to restrict rotation of the piston in the cylinder hole (Ch).