To provide a caster traveling with almost no generation of shocks to both of protruded and recessed parts of a road surface, and a carrier and a truck using the same.

This caster includes a first plate 3 pivotally supporting a first wheel 1 rotatably, a second plate 4 pivotally supporting a second wheel 2 arranged behind the first wheel 1 in a traveling direction rotatably, and a fork pivotally supporting each of the first plate and the second plate coaxially to be rotatable within a vertical plane, and is structured to receive a load transferred from the fork by at least one of the first wheel 1 and the second wheel 2. When the protruded part on the road surface is detected during traveling, the first wheel 1 is brought into an upward rotatable state in order to receive the load only by the second wheel 2 first, and after the protruded part passed under the first wheel 1, the second wheel 2 is brought into the upward rotatable state in order to receive the load only by the first wheel 1.