PURPOSE: To improve the work efficiency of grinding and attain a large contribution to the security of safety, by constituting the grinding head of a surface grinding machine in such a manner that a pivot receives one end part of a head case to 180° inversely support the whole grinding head facing upward.

CONSTITUTION: A wheel shaft 3 mounting a wheel G in the bottom end part and an electric motor 4 are fixed to a base plate 5 with a cover 5a in the internal part of a head case 1a of a grinding head 1. Then the whole unit of the case 1a, as left under the condition that a wheel rotating head 9 is housed in the inside of the case, is 180° inversely turned, capable of disclosing the wheel G and a rotary mechanism in the case 1a facing to the upper, and replacement of the wheel, maintenance and inspection of the head 9 and other work can be neatly performed in a wide space. while a tightening fixture 16 connects the whole unit of the case 1a to be unmovably fixed to the main unit 17 of a machine. By this constitution, the work efficiency of grinding can be improved and a large contribution to the security of safety can be attained.