The present invention refers to an atrial retractor applied for a suitable access to the atrioventricular valves, both mitral and tricuspid, for being replaced by mechanical and/or biological prosthesis. The atrial retractor of the present invention allows a minimum space in the surgery field to be exposed and occupied with a single blade, thus facilitating the free action of the first and second surgeon. The atrial retractor for cardiac valves surgery comprises: a fixing press including a body which first end portion has a quick lock mechanism, and second end portion a jaw with a screw-tab and a single retraction blade consisting of two parts: a handgrip and a blade. The quick lock mechanism allows the blade to be fixed and adjusted, also the fixing mechanism with a jaw and a screw-tab allowing the single blade of retraction to be adjusted to any common sternum retractor, avoiding the use of mobile or articulated parts or additional instruments. The shape of the blade allows the su rgeon to introduce the end portion of the same into the atrium through and incision smaller than the width of the instrument, which upon being rotated over the longitudinal axis thereof in clockwise direction allows the handgrip to be completely slid into the inner portion of the cavity of the patient using the length of the incision without damaging the tissue, so that when the instrument is in it final position allows the valve to be exposed with a wide range of view.La presente invención se refiere a un separador auricular para cirugía de válvulas cardiacas (100) caracterizado porque comprende: un retractor único de separación (110) que consta de dos partes: una barra cilíndrica de sujeción (111) y una valva (112), en uno de los extremos de la barra cilíndrica de sujeción (111) se conforma la base (114) de la valva (112) que tiene dos vertientes formando una "V", los extremos superiores de dichas vertientes se unen por medio de un borde superior (113) de forma semicircular, donde la u
