To keep quality constant, and freely adjust production quantity in assembling a holder, a roller, and an outer ring in a roller shaft bearing.

A supply part for holders 1, a supply part for rollers 3, and a supply part for outer rings are provided as separate bodies, and a means to continuously supply these members one by one while engaging the roller 3 with the holder 1, and a means to then install the outer ring are composed of a pair of rotary plates 15 and pushing rods 16 horizontally movable to advance/retract, so the rotary plates 15 are rotated in one direction while repeating advancing/retracting of the pushing rods 16 to assemble the roller 3 and the holder 1 with the outer ring in order. The pushing rods 16 are composed as a vertically disposed and integrally composed pair to advance/retract simultaneously. The rotary plates 15 comprises the one on which the holder 1 is charged, and the one on which the outer ring is charged, that are integrally connected coaxially.