An electromechanical brake (EMB) may include a nut member coupled to the piston and transferring an axial moving force to the piston; a screw coupled to the nut member and rotated to move the nut member in an axial direction; balls inserted between the nut member and the screw and transferring a rotational force of the screw to the nut member; a compression coil spring having one side mounted on the nut member; and a ball retainer mounted at the other side of the compression coil spring, wherein the ball retainer is disposed to be adjacent to a ball at a rearmost end portion among the balls inserted between the nut member and the screw, and pressurizes the compression coil spring while coming in contact with the balls during braking pressurization.