An example coolant tube block assembly includes a first coolant tube block including at least one of a first coolant flow path tube and a second coolant flow path tube; a hub block configured to expose at least one of the first coolant flow path tube and the second coolant flow path tube on one side, and connected to a lower side of the first coolant tube block; a second coolant tube block including at least one third coolant flow path tube and at least one fourth coolant flow path tube communicating with at least one of the first coolant flow path tube and the second coolant flow path tube, and stacked with the first coolant tube block through the hub block; and a clamp disposed at a lower portion of the second coolant tube block and fastened to a fastening groove formed outside the hub block.