A vertical guide unit is built in modular construction in which a wedge guideway member has raceway grooves cut directly in guideway member while a slider fits over the guideway member for relative movement in a sliding manner. The guideway member has an upper surface extending slantwise with respect to a horizontal lower surface and the raceway grooves are cut slantwise on at least widthwise opposing sides near the upper surface of the guideway member. The slider is recessed at the middle thereof to have widthwise opposing wings to fit over the guideway member for sliding movement. The vertical guide unit is built in between a bed and a table to provide a stage system in which the table is allowed to go up and down as the slider moves in and out relatively to the guideway member.