A length adjustment device, comprising; a head having a cap forming an outside portion and a press button including a pushing piece that is disposed on the cap to be extended toward a lower side; a main pole that includes a fixation shaft that is engaged with the cap and an upper end is inserted into the cap to be fixed thereto, a lever shaft that is built in the fixation shaft, an upper end portion is connected with the press button to be lifted or lowered in accordance with a press or a release of the press button, an upper ball cover that is connected with a lower end portion of the fixation shaft and a first fixation ball is mounted on a first fixation hole that penetrates an external circumferential surface, a first ball lever portion that is connected with a lower end portion of the lever shaft to be lifted or lowered together and at least a part of an external circumferential surface is formed to be recessed such that the first fixation ball is inserted into or drawn out of the upper ball cover, and an upper return spring that is disposed in the fixation shaft and is disposed between the first ball lever portion and the upper ball cover to return the first ball lever portion; and a first extension pole that includes a first movement shaft that is inserted into or out of the main pole and moves between the main pole and the fixation shaft, a plurality of first latching grooves are formed on an interior circumference surface along a length direction, and the movement is locked or unlocked depending on whether the first fixation ball mounted on the upper ball cover is latched or not, a lower ball cover that is attached to a lower end of the first movement shaft and is fitted with a second fixation ball in a second fixation hole penetrated on an external circumferential surface, a second ball lever portion that is installed under the latching groove inside the first movement shaft and contacts the first ball lever portion to move up and down together and at least a portion of an external circumferential surface is recessed so that the second fixation ball is inserted into or drawn out of the lower ball cover, and a lower return spring that is disposed between the lower ball cover and the second ball lever portion to return the second ball lever portion. a head having a cap forming an outside portion and a press button including a pushing piece that is disposed on the cap to be extended toward a lower side; a main pole that includes a fixation shaft that is engaged with the cap and an upper end is inserted into the cap to be fixed thereto, a lever shaft that is built in the fixation shaft, an upper end portion is connected with the press button to be lifted or lowered in accordance with a press or a release of the press button, an upper ball cover that is connected with a lower end portion of the fixation shaft and a first fixation ball is mounted on a first fixation hole that penetrates an external circumferential surface, a first ball lever portion that is connected with a lower end portion of the lever shaft to be lifted or lowered together and at least a part of an external circumferential surface is formed to be recessed such that the first fixation ball is inserted into or drawn out of the upper ball cover, and an upper return spring that is disposed in the fixation shaft and is disposed between the first ball lever portion and the upper ball cover to return the first ball lever portion; and a first extension pole that includes a first movement shaft that is inserted into or out of the main pole and moves between the main pole and the fixation shaft, a plurality of first latching grooves are formed on an interior circumference surface along a length direction, and the movement is locked or unlocked depending on whether the first fixation ball mounted on the upper ball cover is latched or not, a lower ball cover that is attached to a lower end of the first movement shaft and is fitted with a second fixation ball in a second fixation hole penetrated on an external circumferential surface, a second ball lever portion that is installed under the latching groove inside the first movement shaft and contacts the first ball lever portion to move up and down together and at least a portion of an external circumferential surface is recessed so that the second fixation ball is inserted into or drawn out of the lower ball cover, and a lower return spring that is disposed between the lower ball cover and the second ball lever portion to return the second ball lever portion.