A micro device (10, 10') for solid phase extraction comprising: an inlet configured to receive injection of a solvent and a filler; an outlet configured to receive discharging of the solvent; and a dam-forming portion (200, 200') located between the inlet and the outlet; and a dam (210, 210') disposed within the dam-forming portion (200, 200'), the dam (210, 210') configured to allow the solvent to flow therethrough and configured to allow the solvent to be discharged via a side surface of the dam (210, 210') surrounding the portion where the dam is located in the dam-forming portion, but configured to prevent the filler from passing therethrough, wherein in case that the diameter of the dam-forming portion is equal to the diameter of the dam, there is further provided a protruded portion in which the side surface is further protruded so that the protruded portion is configured to allow the solvent to move between the side surface of the dam and the inner surface of the dam-forming portion, or in case that the diameter of the dam is smaller than the diameter of the dam-forming portion, the solvent can pass by the side surface of the dam, wherein each of the dam-forming portion (200, 200') and the dam (210, 210') has a circular cross section with respect to a central axis of the micro device, the central axis extending in a longitudinal direction of the inlet in which the inlet extends, each cross section being perpendicular to the central axis, and wherein the dam-forming portion (200, 200') is configured to accommodate the filler deposited onto the dam (210, 210') in the form of a disk that is centered with respect to the central axis in the dam-forming portion. an inlet configured to receive injection of a solvent and a filler; an outlet configured to receive discharging of the solvent; and a dam-forming portion (200, 200') located between the inlet and the outlet; and a dam (210, 210') disposed within the dam-forming portion (200, 200'), the dam (210, 210') configured to allow the solvent to flow therethrough and configured to allow the solvent to be discharged via a side surface of the dam (210, 210') surrounding the portion where the dam is located in the dam-forming portion, but configured to prevent the filler from passing therethrough, wherein in case that the diameter of the dam-forming portion is equal to the diameter of the dam, there is further provided a protruded portion in which the side surface is further protruded so that the protruded portion is configured to allow the solvent to move between the side surface of the dam and the inner surface of the dam-forming portion, or in case that the diameter of the dam is smaller than the diameter of the dam-forming portion, the solvent can pass by the side surface of the dam, wherein each of the dam-forming portion (200, 200') and the dam (210, 210') has a circular cross section with respect to a central axis of the micro device, the central axis extending in a longitudinal direction of the inlet in which the inlet extends, each cross section being perpendicular to the central axis, and wherein the dam-forming portion (200, 200') is configured to accommodate the filler deposited onto the dam (210, 210') in the form of a disk that is centered with respect to the central axis in the dam-forming portion.