A linear motion device includes: a base that extends in a reference direction; a linear guide mechanism that includes a guide rail fixed to the base and extending in the reference direction and a slider supported movably on the guide rail along the reference direction; a moving body that is fixed to the slider and that is movable in the reference direction together with the slider; a linear motor that includes a stator fixed to the base, the stator including a magnet row and extending in the reference direction, and a mover including a plurality of coils provided with a certain gap from the stator; and a heat transfer body that is disposed between the moving body and the mover and that is connected to the moving body and the mover, and the heat transfer body extends in a direction away from the linear guide mechanism.