A clamp device for wax mold injection molding, comprising: a clamp mechanism section including a mounting table for mounting a mold, a clamp plate, and a clamp drive unit for changing a vertical distance between the mounting table and the clamp plate, and a vertical movement mechanism for vertically moving the clamp mechanism section with respect to a reference surface, the mold being clamped between the mounting table and the clamp plate, characterized in that the clamp device further comprises: a fixed fulcrum whose vertical position is fixed with respect to the clamp drive unit; a movable fulcrum which is vertically movable in unison with the clamp plate; an intermediate fulcrum which is vertically movable at a position spaced horizontally from the fixed fulcrum by 1/n of a horizontal distance between the fixed fulcrum and the movable fulcrum 11(c), wherein the value of n is defined by 1.5≤n≤2.5; a link member having a one end engaged with the movable fulcrum, an other end engaged with the fixed fulcrum, and an intermediate portion between the one end and the other end engaged with the intermediate fulcrum, wherein the vertical movement mechanism vertically moves the clamp mechanism section while keeping the vertical position of the intermediate fulcrum with respect to the reference surface substantially constant. a clamp mechanism section including a mounting table for mounting a mold, a clamp plate, and a clamp drive unit for changing a vertical distance between the mounting table and the clamp plate, and a vertical movement mechanism for vertically moving the clamp mechanism section with respect to a reference surface, the mold being clamped between the mounting table and the clamp plate, characterized in that the clamp device further comprises: a fixed fulcrum whose vertical position is fixed with respect to the clamp drive unit; a movable fulcrum which is vertically movable in unison with the clamp plate; an intermediate fulcrum which is vertically movable at a position spaced horizontally from the fixed fulcrum by 1/n of a horizontal distance between the fixed fulcrum and the movable fulcrum 11(c), wherein the value of n is defined by 1.5≤n≤2.5; a link member having a one end engaged with the movable fulcrum, an other end engaged with the fixed fulcrum, and an intermediate portion between the one end and the other end engaged with the intermediate fulcrum, wherein the vertical movement mechanism vertically moves the clamp mechanism section while keeping the vertical position of the intermediate fulcrum with respect to the reference surface substantially constant. a fixed fulcrum whose vertical position is fixed with respect to the clamp drive unit; a movable fulcrum which is vertically movable in unison with the clamp plate; an intermediate fulcrum which is vertically movable at a position spaced horizontally from the fixed fulcrum by 1/n of a horizontal distance between the fixed fulcrum and the movable fulcrum 11(c), wherein the value of n is defined by 1.5≤n≤2.5; a link member having a one end engaged with the movable fulcrum, an other end engaged with the fixed fulcrum, and an intermediate portion between the one end and the other end engaged with the intermediate fulcrum, wherein the vertical movement mechanism vertically moves the clamp mechanism section while keeping the vertical position of the intermediate fulcrum with respect to the reference surface substantially constant.