The invention relates to a hole-turning device for a part with two parallel holes. A jig plate is arranged on a flange plate of a lathe through an inner hole of the jig plate and fixed by an inner hexagon screw; a part mandrel is arranged on the jig plate; a counterweight mandrel is arranged in a corresponding hole of the jig plate, the axial lines of the part mandrel and the counterweight mandrel are in symmetrical positions of the jig plate rotation center; a counterweight member is arranged on the counterweight mandrel; a bracket is fixed on the counterweight member; a stud is arranged in a screw hole of the bracket and locked by using a nut; the part is arranged on the part mandrel through the inner holes of front and rear ends of the group of machined holes and by using a locating sleeve, a large retaining pad and a countersunk head screw; and the outer circles of middle sections of the other group of holes of the part are pressed on the bracket by using the stud, another nut anda pressure plate. By adopting the hole-turning device for the part with two parallel holes, one of two groups of mutually parallel holes in the part can be easily and quickly machined; moreover, the jig has the advantages of simple structure and convenience for manufacturing.