To provide a wheel rim support device for a tire attachment/detachment device with a simple structure and easy handling.

The wheel rim support device is mounted to the attachment/detachment device MT provided with a base part 10; a control shaft 9 upwardly extending from the base part; a detachable locking means 11 for the wheel rim engageable with the control shaft and a side part of the wheel rim C; and a drive means M for the control shaft. The wheel rim support device is provided with at least a pair of plate-like members 2, 3 abutting on the wheel rim at an opposite side of the locking means, opposed to each other along a center of the control shaft and capable of mutually approaching and retreating; friction engagement means 5, 6, 5a, 5b installed with a deviated angle, partially formed on one and the other of the annular plate-like members and mutually cooperated to retreat the annular plate-like members when an angle of one of the plate-like member is deviated relative to the other plate-like member; and support and rotation motion transmission means 8, 8a between the control shaft and the pair of annular plate-like members.