PURPOSE: To improve the productivity of external circulating type ball screw devices, whose ball circulating tube mounting section can be very easily machined and whose structure is simple without any troublesome adjustment.

CONSTITUTION: A tube abutting groove is formed along a ball circulating tube 4 in a ball nut 2, and a peripheral groove 12 across the tube abutting groove is also formed in the external peripheral face of the ball nut 2. On the other hand, a tube pressing member 15 is of a thin plate, which can be fitted in the peripheral groove 12, and, whose cross section is like a letter, C, and in which a groove 16 fitted with the ball circulating tube 4 is bent at the intermediate section, and has spring-like characteristics.