A particle separation device comprising; inside a plate-like base body, a straight main flow path, a flow inlet and a flow outlet opened in at least one of an upper surface and a lower surface of the base body, a plurality of branch flow paths connected to a portion midway through a side surface of the main flow path in a direction perpendicular to the side surface, a recovery flow path connected to the main flow path, and a disposal flow path connected to the plurality of branch flow paths, wherein the flow inlet includes a sample flow inlet through which a sample which is a fluid containing particles to be separated flows toward the main flow path and a pressing flow inlet connected to a side surface of the main flow path located on an upstream side and opposite to the plurality of branch flow paths in a direction perpendicular to the side surface of the main flow path so that a fluid generating a pressing flow flows through the pressing flow inlet, the flow outlet includes a sample flow outlet connected to the recovery flow path, and at least one disposal flow outlet connected to the main flow path and the disposal flow path, in a planar view of the base body, the sample flow inlet is connected to the main flow path via an R-shaped first bending part, a first straight part, an R-shaped second bending part, and a second straight part, a width in the first bending part and a width in the first straight part are larger than a width in the second bending part and a width in the second straight part, and the width in the second bending part and the width of the second straight part are larger than a width in the main flow path, the pressing flow inlet is connected to the side surface of the main flow path via a third straight part, an R-shaped third bending part, a fourth straight part, and a fifth straight part, and a width in the third straight part is larger than a width in the fourth straight part, and the width in the fourth straight part is larger than a width in the fifth straight part. inside a plate-like base body, a straight main flow path, a flow inlet and a flow outlet opened in at least one of an upper surface and a lower surface of the base body, a plurality of branch flow paths connected to a portion midway through a side surface of the main flow path in a direction perpendicular to the side surface, a recovery flow path connected to the main flow path, and a disposal flow path connected to the plurality of branch flow paths, wherein the flow inlet includes a sample flow inlet through which a sample which is a fluid containing particles to be separated flows toward the main flow path and a pressing flow inlet connected to a side surface of the main flow path located on an upstream side and opposite to the plurality of branch flow paths in a direction perpendicular to the side surface of the main flow path so that a fluid generating a pressing flow flows through the pressing flow inlet, the flow outlet includes a sample flow outlet connected to the recovery flow path, and at least one disposal flow outlet connected to the main flow path and the disposal flow path, in a planar view of the base body, the sample flow inlet is connected to the main flow path via an R-shaped first bending part, a first straight part, an R-shaped second bending part, and a second straight part, a width in the first bending part and a width in the first straight part are larger than a width in the second bending part and a width in the second straight part, and the width in the second bending part and the width of the second straight part are larger than a width in the main flow path, the pressing flow inlet is connected to the side surface of the main flow path via a third straight part, an R-shaped third bending part, a fourth straight part, and a fifth straight part, and a width in the third straight part is larger than a width in the fourth straight part, and the width in the fourth straight part is larger than a width in the fifth straight part.