A screwdriver bit assembly comprising: a sleeve including a front end face, a rear end face, and an outer peripheral face between the front end face and the rear end face, with the sleeve further including a sleeve hole extending from the front end face through the rear end face; a magnetic ring mounted in a front end of the sleeve hole of the sleeve, with the magnetic ring including a through-hole in a central portion thereof; a holding device mounted on the sleeve, providing a holding force towards a longitudinal axis of the sleeve hole; and a screwdriver bit including an insertion end on a front end thereof and a coupling end on a rear end thereof, wherein the coupling end is adapted to couple with an external tool, with the insertion end extending beyond the sleeve and being located in front of the front end face of the sleeve, whereby the screwdriver bit assembly further comprises a retaining ring made of a material more rigid than the sleeve, with the retaining ring mounted in the sleeve hole and being located behind the magnetic ring, and with the retaining ring including a through-hole in a central portion thereof; and the screwdriver bit having a rigidity larger than the sleeve and further including an extending section behind the insertion end, a flange section located behind the extending section and having a diameter larger than a diameter of the extending section, and a clamping section behind the flange section, with the front end of the screwdriver bit extending through the sleeve hole of the. sleeve, the through-hole of the retaining ring, and the through-hole of the magnetic ring, with the flange section having a front side abutting the retaining ring, and with the clamping section held by the holding device. a sleeve including a front end face, a rear end face, and an outer peripheral face between the front end face and the rear end face, with the sleeve further including a sleeve hole extending from the front end face through the rear end face; a magnetic ring mounted in a front end of the sleeve hole of the sleeve, with the magnetic ring including a through-hole in a central portion thereof; a holding device mounted on the sleeve, providing a holding force towards a longitudinal axis of the sleeve hole; and a screwdriver bit including an insertion end on a front end thereof and a coupling end on a rear end thereof, wherein the coupling end is adapted to couple with an external tool, with the insertion end extending beyond the sleeve and being located in front of the front end face of the sleeve, whereby the screwdriver bit assembly further comprises a retaining ring made of a material more rigid than the sleeve, with the retaining ring mounted in the sleeve hole and being located behind the magnetic ring, and with the retaining ring including a through-hole in a central portion thereof; and the screwdriver bit having a rigidity larger than the sleeve and further including an extending section behind the insertion end, a flange section located behind the extending section and having a diameter larger than a diameter of the extending section, and a clamping section behind the flange section, with the front end of the screwdriver bit extending through the sleeve hole of the. sleeve, the through-hole of the retaining ring, and the through-hole of the magnetic ring, with the flange section having a front side abutting the retaining ring, and with the clamping section held by the holding device.