Abstract: The invention has an object to provide a flow path block capable of reducing pressure loss, providing an extremely long flow path and a complex flow path, and achieving weight reduction, and a manufacturing method thereof. A flow path block (1) comprises a block body (11) formed with through holes (21) and a groove (22) communicating with the through holes (21) and a lid member (12) which covers the groove (22). The groove (22) can be formed with any depth and width by a cutting tool to reduce pressure loss. The groove (22) can also be formed in a long shape by the cutting tool, so that a very long flow path can be provided when the groove (22) is covered with the lid member (12). The groove (22) can be made freely by the cutting tool to provide a complex flow path. Further, the thickness of the block body (11) can be reduced to achieve weight reduction.