The present invention relates to a paint-coating brush consisting of a rectangular flat body plate, a handle installed on a center of an upper surface of the body plate, and a plurality of bristles bundled on a lower surface of the body plate, wherein a front end portion of the said plate is bended downward to form a sharp R-shaped muzzle section. The procedures of using the paint-coating brush include: (A) dipping the plurality of bristles in paint; (B) using a front end (tip) portion of the body plate to contact a borderline of a target object and then coating towards a central part of the object being painted. However, the procedure of masking non-coating areas is not included.