The main bag stands independently and moves via free swiveling caster wheels (1) at four corners. A free swiveling caster wheel (1) is provided with a wheel (6), a yoke (7) connected to the wheel (6) in a manner allowing the wheel (6) to rotate, a radial bearing (8) with its outer ring (8B) connected to the yoke (7), a swivel shaft (9) connected to the inner ring (8A) of the radial bearing (8), and a mount (10) which holds the upper end of the swivel shaft (9) fixed. The rotation axis (11) of the wheel (6) is disposed with eccentricity with respect to the swivel axis m, which is the center of rotation of the swivel shaft (9), allowing the yoke (7) to swivel. The yoke (7) and mount (10) have a bend prevention gap established between mutually opposing surfaces in close proximity. When a bending impact load acts on the swivel shaft (9), the yoke (7) and mount (10) press against each other at the bend prevention gap (15) to support the bending impact force.