A linear motion device includes a guide shaft. A to-be-moved member is supported on the guide shaft, and is linearly movable along the guide shaft. A lead screw extends parallel to the guide shaft. A clamper meshes with the lead screw. The clamper moves as the lead screw rotates. An intermediate member is provided between the to-be-moved member and the clamper. An urging member operates for urging the to-be-moved member toward the clamper and enabling the intermediate member to be seated between the to-be-moved member and the clamper in a manner such that an axis of the intermediate member is nonparallel to the guide shaft.