A valve assembly for installation between an inlet pipe and an outlet pipe through which a fluid can be transferred, the valve assembly comprising: a valve body in which an inlet portion, a space portion, and an outlet portion are formed, wherein the inlet portion is connectable to the inlet pipe and the fluid can be introduced through the inlet portion, the fluid can be supplied to an inside of the valve body through the inlet portion stays in the space portion, and the outlet portion is connectable to the outlet pipe and the fluid of the space portion can be discharged to the outside through the outlet portion; and an opening and closing unit configured to open or close a path of the fluid by moving in a state of being in close contact with an inner surface of the valve body, wherein the valve body is formed of a pipe of a steel or stainless-steel material, wherein the valve body is formed with an entrance portion in which the opening and closing unit is installed, wherein the valve body includes the inlet portion formed at one side thereof, the entrance portion formed at the other side thereof, and the space portion formed between the inlet portion and the entrance portion, and the inlet portion, the space portion, and the entrance portion are disposed in a straight line, wherein the opening and closing unit includes: a stem passing through a shielding member installable at the entrance portion; and a disk installed in the stem and slidably movable along a longitudinal direction of the stem in a state in which an outer circumferential surface thereof is in close contact with an inner circumferential surface of the inlet portion or the space portion, a first and second stoppers (261 and 262) formed to protrude along the outer circumferential surface of the stem to restrict the slide movement of the disk; and a handle, which when rotated, linearly moves the stem to move the positions of the first and second stoppers (261 and 261), wherein the stem is arranged in a straight line of the inlet portion, the space portion and the entrance portion, wherein diameters of the inlet portion and/or the space portion are the same in a movement section of the disk, wherein the disk is placed in close contact with the inner circumferential surface of the inlet portion to close the path of the fluid, wherein the first stopper is formed at one side end portion of the stem, wherein the second stopper is formed between the disk and the shielding member. a valve body in which an inlet portion, a space portion, and an outlet portion are formed, wherein the inlet portion is connectable to the inlet pipe and the fluid can be introduced through the inlet portion, the fluid can be supplied to an inside of the valve body through the inlet portion stays in the space portion, and the outlet portion is connectable to the outlet pipe and the fluid of the space portion can be discharged to the outside through the outlet portion; and an opening and closing unit configured to open or close a path of the fluid by moving in a state of being in close contact with an inner surface of the valve body, wherein the valve body is formed of a pipe of a steel or stainless-steel material, wherein the valve body is formed with an entrance portion in which the opening and closing unit is installed, wherein the valve body includes the inlet portion formed at one side thereof, the entrance portion formed at the other side thereof, and the space portion formed between the inlet portion and the entrance portion, and the inlet portion, the space portion, and the entrance portion are disposed in a straight line, wherein the opening and closing unit includes: a stem passing through a shielding member installable at the entrance portion; and a disk installed in the stem and slidably movable along a longitudinal direction of the stem in a state in which an outer circumferential surface thereof is in close contact with an inner circumferential surface of the inlet portion or the space portion, a first and second stoppers (261 and 262) formed to protrude along the outer circumferential surface of the stem to restrict the slide movement of the disk; and a handle, which when rotated, linearly moves the stem to move the positions of the first and second stoppers (261 and 261), a stem passing through a shielding member installable at the entrance portion; and a disk installed in the stem and slidably movable along a longitudinal direction of the stem in a state in which an outer circumferential surface thereof is in close contact with an inner circumferential surface of the inlet portion or the space portion, a first and second stoppers (261 and 262) formed to protrude along the outer circumferential surface of the stem to restrict the slide movement of the disk; and a handle, which when rotated, linearly moves the stem to move the positions of the first and second stoppers (261 and 261), wherein the stem is arranged in a straight line of the inlet portion, the space portion and the entrance portion, wherein diameters of the inlet portion and/or the space portion are the same in a movement section of the disk, wherein the disk is placed in close contact with the inner circumferential surface of the inlet portion to close the path of the fluid, wherein the first stopper is formed at one side end portion of the stem, wherein the second stopper is formed between the disk and the shielding member.