A method for automatically arranging parts on a CAD comprises: part condition acquisition step A; part arrangement order acquisition step; boundary line acquisition step B; part arrangement step C; boundary line updating step; first repetition step; part type change step; and second repetition step. In step A, part boundary condition, set for each of types of parts, representing the type of the part to be permitted to be arranged adjacent to the part is acquired. In step B, boundary line boundary condition to be set for a boundary line parallel to an area termination end line of an arrangement area in X- or Y-direction is acquired. In step C, the part boundary condition set for the part and the boundary line boundary condition set for the boundary line arranged in the arrangement area are compared with each other, and the part is arranged when the conditions match each other.