A swash plate type piston pump capable of changing a discharge capacity according to a load pressure, comprising: a plurality of pistons; a cylinder block including a plurality of cylinders for housing the pistons; a swash plate for reciprocating the pistons to expand and contract volume chambers of the cylinders with the rotation of the cylinder block; a biasing mechanism (21, 22) for biasing the swash plate in a direction to increase a tilting angle; a first control pin for driving the swash plate in a direction to reduce the tilting angle according to a first load pressure; a second control pin for driving the swash plate in a direction to reduce the tilting angle according to a second load pressure, the second control pin being connected with the first control pin in series; and a casing for housing the cylinder block, the pistons, the swash plate, the biasing mechanism (21, 22) and the first and second control pins (31, 32), wherein: the casing includes a pump housing in which a small-diameter hole into which the first control pin is slidably inserted and a large-diameter hole into which the second control pin is slidably inserted are formed on the same axis, and a pump cover provided with a bearing for tiltably supporting the swash plate, the pump cover being mounted on the pump housing; a first pressure chamber to which the first load pressure is introduced is defined between the first control pin and the small-diameter hole; and a second pressure chamber to which the second load pressure is introduced is defined between the second control pin and the large-diameter hole, wherein the small-diameter hole and the large-diameter hole are formed by machining from a side of the pump housing at which the pump cover is mounted before the pump cover is mounted on the pump housing. a plurality of pistons; a cylinder block including a plurality of cylinders for housing the pistons; a swash plate for reciprocating the pistons to expand and contract volume chambers of the cylinders with the rotation of the cylinder block; a biasing mechanism (21, 22) for biasing the swash plate in a direction to increase a tilting angle; a first control pin for driving the swash plate in a direction to reduce the tilting angle according to a first load pressure; a second control pin for driving the swash plate in a direction to reduce the tilting angle according to a second load pressure, the second control pin being connected with the first control pin in series; and a casing for housing the cylinder block, the pistons, the swash plate, the biasing mechanism (21, 22) and the first and second control pins (31, 32), wherein: the casing includes a pump housing in which a small-diameter hole into which the first control pin is slidably inserted and a large-diameter hole into which the second control pin is slidably inserted are formed on the same axis, and a pump cover provided with a bearing for tiltably supporting the swash plate, the pump cover being mounted on the pump housing; a first pressure chamber to which the first load pressure is introduced is defined between the first control pin and the small-diameter hole; and a second pressure chamber to which the second load pressure is introduced is defined between the second control pin and the large-diameter hole, wherein the small-diameter hole and the large-diameter hole are formed by machining from a side of the pump housing at which the pump cover is mounted before the pump cover is mounted on the pump housing. the casing includes a pump housing in which a small-diameter hole into which the first control pin is slidably inserted and a large-diameter hole into which the second control pin is slidably inserted are formed on the same axis, and a pump cover provided with a bearing for tiltably supporting the swash plate, the pump cover being mounted on the pump housing; a first pressure chamber to which the first load pressure is introduced is defined between the first control pin and the small-diameter hole; and a second pressure chamber to which the second load pressure is introduced is defined between the second control pin and the large-diameter hole, wherein the small-diameter hole and the large-diameter hole are formed by machining from a side of the pump housing at which the pump cover is mounted before the pump cover is mounted on the pump housing.