An up-down moving mechanism includes a support member; an up-down moving member that is formed separately from the support member and can be moved up and down with respect to the support member; a screw shaft for moving up and down the up-down moving member; a nut member that is screwed onto the screw shaft; a guide rail that guides the up-down moving member in a vertical direction; a guide block that slidably engages with the guide rail; and a gas spring that includes a cylinder and a piston rod biased in a direction projecting out from the cylinder, and that biases the up-down moving member toward an upper side with respect to the support member. To the support member, the screw shaft is rotatably attached, the guide rail is fixed, and the piston rod is attached.