The present invention pertains to a control device and a control method for controlling a cooling device. The cooling device includes a first cooling water passage for a cylinder head, a second cooling water passage for a cylinder block, a control valve for changing the ratio of the flow volume in the first cooling water passage and the flow volume in the second cooling water passage, and a water pump. The control device controls the control valve so as to increase the ratio of the flow volume in the first cooling water passage when the flow volume of the circulating cooling water is insufficient due to a breakdown of the water pump. Thus, it is possible to suppress damage to the main body of an engine while preventing a decrease in the travel performance of a vehicle when the water pump breaks down.