A 60-year-old man with hypertrophic obstructive cardiomyopathy (HOCM) combined with organic mitral regurgitation underwent transmitral septal myectomy and mitral valve plasty. Although a transaortic septal myectomy (Morrow's procedure) is generally accepted as the standard surgical treatment for HOCM, it may be difficult to perform sufficient septal myectomy for mid-ventricular obstructive hypertrophic cardiomyopathy and apical hypertrophic cardiomyopathy (HCM). The transmitral approach with temporary detachment of the anterior mitral leaflet provides a good surgical view in the left ventricle, which allows sufficient septal myectomy from the outflow tract to the apex.