A paper sheet processing device having a paper currency unit for discriminating sheets of paper inserted or paid out, sorting the discriminated sheets of paper, and storing them, an enclosure having a storage space storing the paper currency unit, and a unit guide mechanism interposed in gaps allowing for horizontal sliding of the enclosure and of the paper currency unit and operating to guide the paper currency unit to pull the paper currency unit into and out of the storage space; characterized in that said unit guide mechanism has a guide portion (152, 172) disposed in a horizontal direction along an inner wall of the enclosure, a guided portion (162, 182) disposed on a side of an outer wall of the paper currency unit movably along the guide portion (152, 172), and a connecting mechanism (168, 188) for connecting together the paper currency unit and the guided portion (162, 182); and wherein said connecting mechanism (168, 188) has distance adjusting portions for varying the distance between the guided portion (162, 182) and the paper currency unit when receiving a horizontal force by movement of the paper currency unit; wherein said connecting mechanism has a connecting member connecting together said guided portion and an outer wall of said paper currency unit; wherein said distance adjusting portions have a securing member being a screw, which is affixed to the connecting member via a tightening hole formed in a horizontal portion of the connecting member, and a slot which is formed in a horizontal portion of a support plate supporting the paper currency unit and in which the securing member is inserted and a spacer (169s, 189s) for forming a gap from the paper currency unit; and wherein the slot has a larger diameter than an outer diameter of the spacer (169s, 189s) in a direction perpendicular to the direction in which the paper currency unit moves, and wherein the securing member then moves through the slot in a direction perpendicular to the direction of motion of the paper currency unit to thereby make variable the sliding gaps. wherein said connecting mechanism (168, 188) has distance adjusting portions for varying the distance between the guided portion (162, 182) and the paper currency unit when receiving a horizontal force by movement of the paper currency unit; wherein said connecting mechanism has a connecting member connecting together said guided portion and an outer wall of said paper currency unit; wherein said distance adjusting portions have a securing member being a screw, which is affixed to the connecting member via a tightening hole formed in a horizontal portion of the connecting member, and a slot which is formed in a horizontal portion of a support plate supporting the paper currency unit and in which the securing member is inserted and a spacer (169s, 189s) for forming a gap from the paper currency unit; and wherein the slot has a larger diameter than an outer diameter of the spacer (169s, 189s) in a direction perpendicular to the direction in which the paper currency unit moves, and wherein the securing member then moves through the slot in a direction perpendicular to the direction of motion of the paper currency unit to thereby make variable the sliding gaps.