To provide a double row tapered roller bearing unit, which is easy to fabricate with satisfactory assembling accuracy, and further allows easy preload management and preload readjustment.

Both outside inner ring elements 14, 14 preload each conical roller 16, 16 of an outside bearing 2 by being pressed from both sides in axial direction by an outward flange-like collar portion 30 formed on the outer periphery at one end of both axial ends of an inside outer ring member 22 and a presser ring 31 attached to the other end thereof, thereby preloading each conical roller 16, 16 of an outside bearing 2. Both inside inner ring elements 24, 24 hold an inner ring-to-inner ring seat 60 between the pair of inside inner ring elements 24, and preload each conical roller of an inside bearing 3 by the effect of pressing forces from both sides in axial direction by an outward flange-like other collar portion 41 formed on the outer periphery on one axial end side of a shaft part 40 and a nut member 43 screwed to the other end side of the shaft part 42.