A manufacturing method for a cooling unit that includes a cooling plate in which a cooling fluid flows, the cooling plate having a cooling pipe through which the cooling fluid flows, and a pair of tabular members arranged to be opposed to each other across the cooling pipe, the manufacturing method for a cooling unit includes: forming a groove in which the cooling pipe is housed at least in one opposed surface of the pair of tabular members; combining the pair of tabular members while housing the cooling pipe in the groove; and filling a heat conduction material in a gap between the groove and the cooling pipe.