A parison separation device comprising: a cutter with a cutting edge, the cutting edge extending in a one direction and facing upward; and a block, the cutter being attached to an upper part of the block, inclined surfaces being formed on both sides of the block in a thickness direction of the cutting edge, each of the inclined surfaces including a component that is inclined increasingly downward as it gets closer to one direction side end, wherein the parison separation device is disposed on a discharging direction side of a discharging port of a parison and configured to cut the parison discharged from the discharging port, wherein the one direction side is a radius direction from a central axis toward an outer side in a plane orthogonal to the central axis, the central axis being parallel to a vertical direction in the discharging port, the discharging port having an annular shape when the parison is discharged from a gap between a die including a through hole and a core inserted inside the through hole, the cutter is disposed on the discharging direction side of the discharging port and disposed so as to cross the discharging port, and is configured to cut the parison discharged from the discharging port, and the block separates the cut parison and forms it into a sheet, characterized in that the block comprises: a cutter support part extending in the one direction and has a plate-like shape in which plate surfaces face in the thickness direction, the cutter being disposed on a top surface of the cutter support part extending in the one direction; and an attachment part with a side surface joined to a side of the block opposite to a side thereof on the one direction side, and the inclined surfaces are disposed so that they sandwich the cutter through the plate surfaces on both sides of the cutter support part, a top surface of the attachment part is attached to a bottom surface of the core, and an upper end of the cutting edge is in contact with the bottom surface of the core. a cutter with a cutting edge, the cutting edge extending in a one direction and facing upward; and a block, the cutter being attached to an upper part of the block, inclined surfaces being formed on both sides of the block in a thickness direction of the cutting edge, each of the inclined surfaces including a component that is inclined increasingly downward as it gets closer to one direction side end, wherein the parison separation device is disposed on a discharging direction side of a discharging port of a parison and configured to cut the parison discharged from the discharging port, wherein the one direction side is a radius direction from a central axis toward an outer side in a plane orthogonal to the central axis, the central axis being parallel to a vertical direction in the discharging port, the discharging port having an annular shape when the parison is discharged from a gap between a die including a through hole and a core inserted inside the through hole, the cutter is disposed on the discharging direction side of the discharging port and disposed so as to cross the discharging port, and is configured to cut the parison discharged from the discharging port, and the block separates the cut parison and forms it into a sheet, characterized in that the block comprises: a cutter support part extending in the one direction and has a plate-like shape in which plate surfaces face in the thickness direction, the cutter being disposed on a top surface of the cutter support part extending in the one direction; and an attachment part with a side surface joined to a side of the block opposite to a side thereof on the one direction side, and the inclined surfaces are disposed so that they sandwich the cutter through the plate surfaces on both sides of the cutter support part, a top surface of the attachment part is attached to a bottom surface of the core, and an upper end of the cutting edge is in contact with the bottom surface of the core. a cutter support part extending in the one direction and has a plate-like shape in which plate surfaces face in the thickness direction, the cutter being disposed on a top surface of the cutter support part extending in the one direction; and an attachment part with a side surface joined to a side of the block opposite to a side thereof on the one direction side, and the inclined surfaces are disposed so that they sandwich the cutter through the plate surfaces on both sides of the cutter support part, a top surface of the attachment part is attached to a bottom surface of the core, and an upper end of the cutting edge is in contact with the bottom surface of the core.