The present invention provides a low cost coolant container that is easy to produce without decreasing its ability to maintain a coolant. The coolant container 1 comprises an outer container 11 and an inner container 12 wherein the cylindrical members 111 and 121 and the plate members 112 and 122 of the outer container 11 and the inner container 12 are engaged at the peripheral end such that even if an external force acts on the flat surface of the plate members 112 and 122 the stopping means 111a and 121a of the engaging portions A and B prevent the plate members 112 and 122 from sinking toward the hollow portion 13 side by supporting the plate members 112 and 122 and resisting the external force and as a result the container has the required structural strength and its ability to maintain a coolant is preserved. Moreover, because cylindrical members 111 and 121 and plate members 112 and 122 with simple shapes are used, it is not necessary to strengthen them by screwing the plate members 112 and 122 into the cylindrical members 111 and 121, and these material and processing costs can be avoided and a low cost product can be provided.