PURPOSE: To prevent noise generation without need for any additional space by displacing both half bodies of piston parts by an appropriate angle mutually, thus canceling maximum amplitude areas each other.

CONSTITUTION: This external axis rotary piston blower involves two mutually intersecting cylindrical peripheral running passages 6 and pistons 7, 8 having axially concentric running surfaces, and the pistons running, brought into contact with the cylindrical peripheral running passages 6 and axially concentric cylindrical surfaces of smaller curvature radius against the respective opposing piston to run, wherein the pistons 7, 8 are divided into two identical half bodies 9, 10, 11, 12 in a radial plane. Both half bodies 9, 10 of one piston 7 are displaced with respect to one another by 25° to 45°, preferably 35°, and both half bodies 11, 12 of the other piston 8 are displaced in the opposite direction by an equal angle around the rotational axis of a piston axis.