In patients with midventricular obstructive hypertrophic cardiomyopathy (HCM), a transapical approach allows excellent exposure for midventricular myectomy. Although the ventriculotomy is required on the antero-lateral left ventricular wall, the minimal ventriculotomy would be ideal, especially for cases with concomitant apical aneurysm. We report a case of midventricular obstructive HCM with concomitant apical aneurysm. Through the minimal ventriculotomy within the aneurysm, the hypertrophic septum was successfully hollowed out under repeated ultrasound guidance. Intraoperative ultrasound guidance is useful for transapical septal myectomy in midventricular obstructive HCM.