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 does not pass through the inside of the engine; and (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, the cooling water control apparatus comprising: a detecting device configured to detect a first temperature (thw) of the cooling water in a pipe portion of the first pipe, the pipe portion being located between the engine and the switching valve; and a determining device configured to determine that there is a failure of the switching valve whose state is the closed state, if a required period which is required from the output of the command for changing the state of the switching valve from the opened state to the closed state until the first temperature reaches a temperature for the determination which is higher than the first temperature is larger than a period for the determination, characterised in the switching valve being 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 to close 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 determin that there is a failure of the micro flowing portion, if the required time is larger than the period for the determination. (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 does not pass through the inside of the engine; and (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, a detecting device configured to detect a first temperature (thw) of the cooling water in a pipe portion of the first pipe, the pipe portion being located between the engine and the switching valve; and a determining device configured to determine that there is a failure of the switching valve whose state is the closed state, if a required period which is required from the output of the command for changing the state of the switching valve from the opened state to the closed state until the first temperature reaches a temperature for the determination which is higher than the first temperature is larger than a period for the determination, characterised in the switching valve being 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 to close 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 determin that there is a failure of the micro flowing portion, if the required time is larger than the period for the determination. (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 to close 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,