A heat sink for a power module able to realize a further improvement of heat radiating performance and a further improvement of a mounting property is provided.The heat sink 1 for a power module has a laminating body 20, a first side plate 30 and a second side plate 40. The laminating body 20 has plural flow path plates 21 formed in a plate shape in which plural grooves 23 parallel to each other are concavely arranged on a flat joining face 22. Each groove 23 is set to a parallel flow path 50 parallel to a front face side by laminating each flow path plate 21 by each joining face 22. A portion other than each groove 23 of each joining face 22 forms a heat transfer path 70a to each parallel flow path 50 of a laminating direction. A flow-in path 30a and a flow-out path 40a are formed in the first and second side plates 30, 40. The flow-in path 30a and the flow-out path 40a are joined to side faces 26a, 26b of the laminating body 20, and are communicated with each parallel flow path 50. The flow-in path 30a flows a cooling medium into each parallel flow path 50. The flow-out path 40a flows the cooling medium out of each parallel flow path 50. A refrigerant flow path is constructed by the flow-in path 30a, each parallel flow path 50 and the flow-out path 40a.