A multi-link piston crank mechanism for an internal combustion engine, the multi-link piston crank mechanism comprising: a lower link including a crank pin bearing portion which is rotatably mounted to a crank pin of a crank shaft; an upper link including a first end portion connected to a piston pin of a piston, and a second end portion connected to a first end side of the lower link through a first link pin inserted into a first through hole of the second end portion of the upper link; and a control link including a first end portion supported by a cylinder block, and a second end portion connected to the second end side of the lower link through a second link pin inserted into a second through hole of the second end portion of the control link; the lower link including the first end side to which an input load due to a combustion load is acted, the lower link including a bifurcated first end side protruding piece portion and a bifurcated second end side protruding piece portion which are positioned on both sides of the crank pin bearing portion when viewed from an axial direction of the crank shaft, the bifurcated first end side protruding piece portion sandwiching the second end of the upper link, and the bifurcated second end side protruding piece portion sandwiching the second end of the control link, the crank pin bearing portion including a central portion in the axial direction of the crank shaft, the central portion having a thickness along a radial direction of the crank pin, the thickness of the central portion at a portion positioned on the first end side of the lower link being larger than a thickness of a portion positioned on the second end side of the lower link, and a thickness of the control link second end portion along a radial direction of the second through hole being larger than a thickness of the upper link second end portion along a radial direction of the first through hole, wherein: the bifurcated first end side protruding piece portion of the lower link comprises a pair of walls being held apart to sandwich the second end portion of the upper link and each including a first through hole to insert the first link pin, and the bifurcated second end side protruding piece portion of the lower link comprises a pair of walls being held apart to sandwich the second end portion of the control link and each including a second through hole to insert the second link pin, and a plurality of bolts holding the two parts of the lower link together are located between the pair of walls. a lower link including a crank pin bearing portion which is rotatably mounted to a crank pin of a crank shaft; an upper link including a first end portion connected to a piston pin of a piston, and a second end portion connected to a first end side of the lower link through a first link pin inserted into a first through hole of the second end portion of the upper link; and a control link including a first end portion supported by a cylinder block, and a second end portion connected to the second end side of the lower link through a second link pin inserted into a second through hole of the second end portion of the control link; the lower link including the first end side to which an input load due to a combustion load is acted, the lower link including a bifurcated first end side protruding piece portion and a bifurcated second end side protruding piece portion which are positioned on both sides of the crank pin bearing portion when viewed from an axial direction of the crank shaft, the bifurcated first end side protruding piece portion sandwiching the second end of the upper link, and the bifurcated second end side protruding piece portion sandwiching the second end of the control link, the crank pin bearing portion including a central portion in the axial direction of the crank shaft, the central portion having a thickness along a radial direction of the crank pin, the thickness of the central portion at a portion positioned on the first end side of the lower link being larger than a thickness of a portion positioned on the second end side of the lower link, and a thickness of the control link second end portion along a radial direction of the second through hole being larger than a thickness of the upper link second end portion along a radial direction of the first through hole, wherein: the bifurcated first end side protruding piece portion of the lower link comprises a pair of walls being held apart to sandwich the second end portion of the upper link and each including a first through hole to insert the first link pin, and the bifurcated second end side protruding piece portion of the lower link comprises a pair of walls being held apart to sandwich the second end portion of the control link and each including a second through hole to insert the second link pin, and a plurality of bolts holding the two parts of the lower link together are located between the pair of walls. the bifurcated first end side protruding piece portion of the lower link comprises a pair of walls being held apart to sandwich the second end portion of the upper link and each including a first through hole to insert the first link pin, and the bifurcated second end side protruding piece portion of the lower link comprises a pair of walls being held apart to sandwich the second end portion of the control link and each including a second through hole to insert the second link pin, and a plurality of bolts holding the two parts of the lower link together are located between the pair of walls.