An eco-friendly pumping device using a principle of vacuum, comprising: a press pumping unit including a dispensing head, a pump cylinder and a duct, the dispensing head being connected to a top end of the pump cylinder, the duct being connected to a bottom end of the pump cylinder, a cap being disposed close to a top end of the pump cylinder; a replaceable soft bag including a flexible bag body and an opening part formed on a top end of the flexible bag body, the flexible bag body being filled with fluid material, wherein the pump cylinder of the press pumping unit is, together with the duct, inserted in the opening part of the replaceable soft bag, so as to seal the opening part of the replaceable soft bag, and forms a closed space in an interior of the replaceable soft bag; wherein the interior of the replaceable soft bag is capable of being in a negative pressure state simultaneously when operating the dispensing head because of vacuum effect, and the shape and an inner volume of the flexible bag body is squeezed automatically by external air pressure outside because of vacuum effect as the time of use and amount of use increase; wherein the duct extends into the replaceable soft bag so that the lower end of the duct is close to a bottom wall of the replaceable soft bag, the fluid material being in contact and surrounding the lower end of the duct; and a bottle having a bottle lip formed on a top end thereof, the replaceable soft bag being disposed in the bottle, and the cap of the press pumping unit being connected to the bottle lip of the bottle; wherein when the dispensing head of the press pumping unit is pressed, the pump cylinder is capable of producing a drawing force, and the interior of the replaceable soft bag forms a negative pressure state, so that the fluid material is capable of being outputted through the duct by the vacuum effect, wherein the pump cylinder has at least one first fastening portion radially formed on a radially external circumferential surface of the pump cylinder, the opening part has at least one second fastening portion radially formed on a radially internal circumferential surface of the opening part, and the first fastening portion of the pump cylinder and the second fastening portion of the opening part are fastened to each other in a radial direction of the pump cylinder by relatively moving the first fastening portion and the second fastening portion along an axial direction of the pump cylinder and relatively rotating the first fastening portion and the second fastening portion about the axial direction of the pump cylinder, so that the replaceable soft bag is fastened to the press pumping unit. a press pumping unit including a dispensing head, a pump cylinder and a duct, the dispensing head being connected to a top end of the pump cylinder, the duct being connected to a bottom end of the pump cylinder, a cap being disposed close to a top end of the pump cylinder; a replaceable soft bag including a flexible bag body and an opening part formed on a top end of the flexible bag body, the flexible bag body being filled with fluid material, wherein the pump cylinder of the press pumping unit is, together with the duct, inserted in the opening part of the replaceable soft bag, so as to seal the opening part of the replaceable soft bag, and forms a closed space in an interior of the replaceable soft bag; wherein the interior of the replaceable soft bag is capable of being in a negative pressure state simultaneously when operating the dispensing head because of vacuum effect, and the shape and an inner volume of the flexible bag body is squeezed automatically by external air pressure outside because of vacuum effect as the time of use and amount of use increase; wherein the duct extends into the replaceable soft bag so that the lower end of the duct is close to a bottom wall of the replaceable soft bag, the fluid material being in contact and surrounding the lower end of the duct; and a bottle having a bottle lip formed on a top end thereof, the replaceable soft bag being disposed in the bottle, and the cap of the press pumping unit being connected to the bottle lip of the bottle; wherein when the dispensing head of the press pumping unit is pressed, the pump cylinder is capable of producing a drawing force, and the interior of the replaceable soft bag forms a negative pressure state, so that the fluid material is capable of being outputted through the duct by the vacuum effect, wherein the pump cylinder has at least one first fastening portion radially formed on a radially external circumferential surface of the pump cylinder, the opening part has at least one second fastening portion radially formed on a radially internal circumferential surface of the opening part, and the first fastening portion of the pump cylinder and the second fastening portion of the opening part are fastened to each other in a radial direction of the pump cylinder by relatively moving the first fastening portion and the second fastening portion along an axial direction of the pump cylinder and relatively rotating the first fastening portion and the second fastening portion about the axial direction of the pump cylinder, so that the replaceable soft bag is fastened to the press pumping unit.