A surface of a plate (102) having a predetermined thickness is used as a cooling surface (101). A pair of cooling medium entrance and exit (111, 112) are provided on one end surface (102a). First and second cooling medium flow paths (131, 132), a cooling medium branch path (121) communicating with the cooling medium entrance (111) and used for dividing cooling medium to flow into the cooling medium flow paths (131, 132), and a cooling medium merging path (122) at which the cooling media flowing from the exits of the cooling medium flow paths (131, 132) merge, are formed on a surface opposite to the cooling surface (101). The cooling medium flowing clockwise through the first cooling medium flow path (131) passes through a cooling medium communicating flow path (123) formed so as to three-dimensionally cross the first cooling medium flow path (131), so that the cooling medium flowing counterclockwise through the second cooling medium flow path (132) and the cooling medium flowing through the first cooling medium flow path (131) flow into the cooling medium merging path (122). Thus, pressure loss is avoided, high cooling performance is obtained, and simplification of a cooling system including a cooling medium pipe and the like can be realized.