A paper sheet storage apparatus comprising: a placement mount on which paper sheets are placed; a leading-edge position restriction guide that restricts a position of a leading edge portion of a paper sheet in an entering direction in which the paper sheet advances when being transported onto the placement mount; a sensor that detects presence/absence of an accumulation space for paper sheets that is located above the placement mount; and a pressing part disposed to be swingable, wherein when a paper sheet is being transported on the placement mount, the pressing part functions as a guide configured to prevent the paper sheets from entering the space upward of the leading-edge position restriction guide, wherein the sensor is configured to detect the presence/absence of the accumulation space by using detection light emitted to a space between a first position that is located on an opposite side of the leading-edge position restriction guide from the paper sheets on the placement mount and a second position below the first position that is located on an opposite side of the paper sheets on the placement mount from the leading-edge position restriction guide, the first position is located above the upper edge of the accumulation space, and the detection light is emitted to travel above the accumulation space from a leading - edge side of the paper sheets on the placement mount, characterised in that the pressing part either is disposed at a position in the width direction orthogonal to the entering direction at which the pressing part does not interfere with the detection light, or includes a through hole through which the detection light passes, and the sensor is configured, if a paper sheet leaning against the leading - edge position restriction guide lifts the pressing part lowered under its weight and the leading - edge portion of the paper sheet reaches a position above the upper edge of the accumulation space, to detect that a sufficient accumulation space is not present. a placement mount on which paper sheets are placed; a leading-edge position restriction guide that restricts a position of a leading edge portion of a paper sheet in an entering direction in which the paper sheet advances when being transported onto the placement mount; a sensor that detects presence/absence of an accumulation space for paper sheets that is located above the placement mount; and a pressing part disposed to be swingable, wherein when a paper sheet is being transported on the placement mount, the pressing part functions as a guide configured to prevent the paper sheets from entering the space upward of the leading-edge position restriction guide, wherein the sensor is configured to detect the presence/absence of the accumulation space by using detection light emitted to a space between a first position that is located on an opposite side of the leading-edge position restriction guide from the paper sheets on the placement mount and a second position below the first position that is located on an opposite side of the paper sheets on the placement mount from the leading-edge position restriction guide, the first position is located above the upper edge of the accumulation space, and the detection light is emitted to travel above the accumulation space from a leading - edge side of the paper sheets on the placement mount, characterised in that the pressing part either is disposed at a position in the width direction orthogonal to the entering direction at which the pressing part does not interfere with the detection light, or includes a through hole through which the detection light passes, and the sensor is configured, if a paper sheet leaning against the leading - edge position restriction guide lifts the pressing part lowered under its weight and the leading - edge portion of the paper sheet reaches a position above the upper edge of the accumulation space, to detect that a sufficient accumulation space is not present.