In a transmission control device for controlling a transmission, a controller determines failure of a SOL corresponding to a hydraulic secondary-pressure actuator. The controller variably controls line command pressure, and in a case where the failure is determined, fixes the line command pressure to a line pressure set value. The controller variably controls primary command pressure, and in a case where the failure is determined, continuously changes a speed ratio of a variator by variably controlling the primary command pressure. The controller variably controls secondary command pressure, and in a case where the failure is determined, fixes the secondary command pressure to a secondary pressure set value.