A semiconductor module and a cooler capable of cooling a semiconductor element efficiently. The semiconductor module supplies a refrigerant to a water jacket configuring the cooler, to cool a circuit element part disposed on an outer surface of a fin base. This semiconductor module has: a fin connected thermally to the circuit element part; a refrigerant introducing passage in the water jacket, which has a guide part that has one surface and another surface inclined to guide the refrigerant toward one side surface of the fin; a refrigerant discharge passage disposed in the water jacket to be parallel to the refrigerant introducing passage, which has a side wall parallel to another side surface of the fin; and a cooling passage formed in a position for communicating the refrigerant introducing passage and the refrigerant discharge passage with each other in the water jacket. The fin is disposed in the cooling passage.