Abstract: A caster of an endless structure is provided which is almost jam-proof even in the case of a bigger gap. The caster includes a first wheel supported on a mounting leg, a second wheel supported by an axle on one end of a suspension arm of which the other end is supported by an axle which also supports the first wheel, and a wrap-around member which is wrapped around the first and second wheels. The wraparound member is formed an endless belt form by connecting independent pieces to each other. The outer peripheral section of each piece is provided with a wider section and when the wraparound member is depressed and warps, the wider section is adapted to touch a wider section of the adjacent piece, thereby preventing further depression.