Disclosed is a stator structure of a rotary device and its forming method. The method for forming a stator structure includes the steps of (a) forming a first part having a first middle portion with a through hole, and M pieces of extending portions extending from the first middle portion, (b) forming a second part having a second middle portion with a through hole, and N pieces of extending portions extending from the second middle portion, (c) alternately bending the M pieces of extending portions of the first part toward a first direction and alternately bending the N pieces of extending portions of the second part toward a second direction opposite to the first direction, respectively, and (d) correspondingly combining the first and second parts together to form the stator structure in which the bent extending portions of the first and second parts constitute an enclosed columnar portion of the stator structure for winding a coil thereon, and (e) winding a coil around the enclosed columnar portion, wherein M and N are even numbers not less than four, respectively.