A positioning arm apparatus for an ultrasound head, the positioning arm apparatus comprising: a first link provided with a first j oint at a lower end of one side thereof and a second joint at an upper end of the other side thereof rotatable left and right about a center of a vertical axis of the first joint; a second link connected to the first link based on the second joint, rotatable left and right about a vertical axis of the second joint, and tiltable up and down about a horizontal axis of the second joint; a first mechanical mechanism provided to the first link and configured to simultaneously fix rotational motions of the first link and the second link or release at least one of the fixed first link and the second link for the rotational motion; and a head connection unit provided at one end of the second link and connected to an ultrasound head, characterized in that: the first mechanical mechanism comprises: a first lever; a worm gear configured to rotate in a horizontal direction by rotation of the first lever; a first worm and a second worm connected to both sides relative to the worm gear and configured to rotate in a vertical direction by the rotation of the worm gear in the horizontal direction; a first shaft and a second shaft connected to the respective worm wheels and each configured to rotate in the same direction as the connected worm wheel by the rotation of the worm wheel; a first tightener and a second tightener configured to tighten or loosen the respective shaft holders (35a, 35b) by the rotation of the respective shafts (33a, 33b); and a first rotation axis and a second rotation axis respectively inserted into holes of the respective shaft holders, fixed to the respective joints, and configured to be simultaneously fixed or released by fastening or loosening the respective shaft holders. a first link provided with a first j oint at a lower end of one side thereof and a second joint at an upper end of the other side thereof rotatable left and right about a center of a vertical axis of the first joint; a second link connected to the first link based on the second joint, rotatable left and right about a vertical axis of the second joint, and tiltable up and down about a horizontal axis of the second joint; a first mechanical mechanism provided to the first link and configured to simultaneously fix rotational motions of the first link and the second link or release at least one of the fixed first link and the second link for the rotational motion; and a head connection unit provided at one end of the second link and connected to an ultrasound head, characterized in that: the first mechanical mechanism comprises: a first lever; a worm gear configured to rotate in a horizontal direction by rotation of the first lever; a first worm and a second worm connected to both sides relative to the worm gear and configured to rotate in a vertical direction by the rotation of the worm gear in the horizontal direction; a first shaft and a second shaft connected to the respective worm wheels and each configured to rotate in the same direction as the connected worm wheel by the rotation of the worm wheel; a first tightener and a second tightener configured to tighten or loosen the respective shaft holders (35a, 35b) by the rotation of the respective shafts (33a, 33b); and a first rotation axis and a second rotation axis respectively inserted into holes of the respective shaft holders, fixed to the respective joints, and configured to be simultaneously fixed or released by fastening or loosening the respective shaft holders. a first lever; a worm gear configured to rotate in a horizontal direction by rotation of the first lever; a first worm and a second worm connected to both sides relative to the worm gear and configured to rotate in a vertical direction by the rotation of the worm gear in the horizontal direction; a first shaft and a second shaft connected to the respective worm wheels and each configured to rotate in the same direction as the connected worm wheel by the rotation of the worm wheel; a first tightener and a second tightener configured to tighten or loosen the respective shaft holders (35a, 35b) by the rotation of the respective shafts (33a, 33b); and a first rotation axis and a second rotation axis respectively inserted into holes of the respective shaft holders, fixed to the respective joints, and configured to be simultaneously fixed or released by fastening or loosening the respective shaft holders.