A cooling water control apparatus for controlling a cooling apparatus, the cooling apparatus being provided with: (i) a first pipe (181a, 181b, 181c, 181d) configured to circulate a cooling water and which passes through an inside of an engine; (ii) a second pipe (182a, 182b, 182c, 182d) configured to circulate the cooling water and which bypasses the inside of the engine; (iii) a switching valve which is disposed at a downstream side of the engine, a state of the switching valve being changed between an opened state and a closed state in accordance with a command, the opened state allowing a first flow amount of cooling water to flow from the first pipe to the second pipe, the closed state allowing a second flow amount of cooling water to flow from the first pipe to the second pipe, the second flow amount being less than the first flow amount; and (iv) a supplying mechanism configured to supply the cooling water to the first and second pipes, the cooling water control apparatus comprising: a determining device configured to determine whether or not there is a failure of the switching valve on the basis of a difference (ΔTsens) between a first temperature (thw) of the cooling water in the first pipe and a second temperature (thb) of the cooling water in the second pipe after the command for changing the state of the switching valve from the closed state to the opened state is outputted; the switching valve is provided with: (i) a valve portion configured to open a passage between the first and second pipes such that the first flow amount of the cooling water flows from the first pipe to the second pipe when the state of the switching valve is the opened state and which closes the passage between the first and second pipes when the state of the switching valve is the closed state; and (ii) a micro flowing portion (13b, 13c) configured to allow the second flow amount of the cooling water to flow from the first pipe to the second pipe when the state of the switching valve is the closed state, the determining device being configured to determine whether or not there is a failure of the valve portion, the cooling water control apparatus being characterized in that it further comprises a controlling device configured to control the supplying mechanism to supply the cooling water even after the engine stops, when the engine stops while the determining device is determining whether or not there is the failure of the switching valve. (i) a first pipe (181a, 181b, 181c, 181d) configured to circulate a cooling water and which passes through an inside of an engine; (ii) a second pipe (182a, 182b, 182c, 182d) configured to circulate the cooling water and which bypasses the inside of the engine; (iii) a switching valve which is disposed at a downstream side of the engine, a state of the switching valve being changed between an opened state and a closed state in accordance with a command, the opened state allowing a first flow amount of cooling water to flow from the first pipe to the second pipe, the closed state allowing a second flow amount of cooling water to flow from the first pipe to the second pipe, the second flow amount being less than the first flow amount; and (iv) a supplying mechanism configured to supply the cooling water to the first and second pipes, a determining device configured to determine whether or not there is a failure of the switching valve on the basis of a difference (ΔTsens) between a first temperature (thw) of the cooling water in the first pipe and a second temperature (thb) of the cooling water in the second pipe after the command for changing the state of the switching valve from the closed state to the opened state is outputted; the switching valve is provided with: (i) a valve portion configured to open a passage between the first and second pipes such that the first flow amount of the cooling water flows from the first pipe to the second pipe when the state of the switching valve is the opened state and which closes the passage between the first and second pipes when the state of the switching valve is the closed state; and (ii) a micro flowing portion (13b, 13c) configured to allow the second flow amount of the cooling water to flow from the first pipe to the second pipe when the state of the switching valve is the closed state, (i) a valve portion configured to open a passage between the first and second pipes such that the first flow amount of the cooling water flows from the first pipe to the second pipe when the state of the switching valve is the opened state and which closes the passage between the first and second pipes when the state of the switching valve is the closed state; and (ii) a micro flowing portion (13b, 13c) configured to allow the second flow amount of the cooling water to flow from the first pipe to the second pipe when the state of the switching valve is the closed state, the determining device being configured to determine whether or not there is a failure of the valve portion,