A filtration apparatus, comprising: a plurality of hollow filter sheets each obtained by stacking two filters and connecting outer peripheral edges thereof; and a suction pipe extending through the plurality of hollow filter sheets and connected to a hollow portion of each hollow filter sheet, wherein the filtration apparatus filters liquid by transferring, from the hollow portion of the hollow filter sheet to the suction pipe, liquid penetrating from an outside of the hollow filter sheet to an inside of the hollow portion, wherein the suction pipe includes a suction hole connected to the hollow portion of the hollow filter sheet, wherein the hollow filter sheet includes a through hole through which the suction pipe is inserted, the through holes having the suction pipe inserted therethrough, thereby connecting the plurality of hollow filter sheets to the suction pipe in a stacked manner, wherein a ring-shaped packing is clamped between the stacked hollow filter sheets having the suction pipe inserted therethrough, the ring-shaped packing having an inner shape allowing the suction pipe to be inserted therethrough and an outer shape longer than an inner shape of the through hole of the hollow filter sheet, the ring-shaped packing watertightly sealing a gap between the hollow filter sheet and the suction pipe, wherein the hollow filter sheet is provided with the hollow portion between the two filters, the hollow portion being provided with a spacer with a surface having pits and projections, characterized in that a narrow passage space allowing liquid to pass through is provided between the filter and the spacer by pressing the two filters against surfaces of the spacer with the ring-shaped packings and causing the filters to be deformed into a shape according to the surfaces of the spacer, the narrow passage space being smaller than a drainage space between the filters and the spacer that are not clamped by the ring-shaped packings. a plurality of hollow filter sheets each obtained by stacking two filters and connecting outer peripheral edges thereof; and a suction pipe extending through the plurality of hollow filter sheets and connected to a hollow portion of each hollow filter sheet, wherein the filtration apparatus filters liquid by transferring, from the hollow portion of the hollow filter sheet to the suction pipe, liquid penetrating from an outside of the hollow filter sheet to an inside of the hollow portion, wherein the suction pipe includes a suction hole connected to the hollow portion of the hollow filter sheet, wherein the hollow filter sheet includes a through hole through which the suction pipe is inserted, the through holes having the suction pipe inserted therethrough, thereby connecting the plurality of hollow filter sheets to the suction pipe in a stacked manner, wherein a ring-shaped packing is clamped between the stacked hollow filter sheets having the suction pipe inserted therethrough, the ring-shaped packing having an inner shape allowing the suction pipe to be inserted therethrough and an outer shape longer than an inner shape of the through hole of the hollow filter sheet, the ring-shaped packing watertightly sealing a gap between the hollow filter sheet and the suction pipe, wherein the hollow filter sheet is provided with the hollow portion between the two filters, the hollow portion being provided with a spacer with a surface having pits and projections, characterized in that a narrow passage space allowing liquid to pass through is provided between the filter and the spacer by pressing the two filters against surfaces of the spacer with the ring-shaped packings and causing the filters to be deformed into a shape according to the surfaces of the spacer, the narrow passage space being smaller than a drainage space between the filters and the spacer that are not clamped by the ring-shaped packings.