During a shifting operation that a first engaging element is changed from an engaged state to a disengaged state, a fail-safe valve is used to forcibly drain a first engaging-element pressure from the first engaging element by using a second engaging-element pressure applied to a second engaging element brought into an engaging state from a releasing state. The fail-safe valve includes a spool and uses the second engaging-element pressure acting on the spool in one axial direction and an opposing pressure acting on the spool in the opposing direction as operating signal pressures. The fail-safe valve is switchable to a drain position, when the second engaging-element pressure is regulated toward a specified fail-safe valve operating point pressure higher than a maximum pressure value of the second engaging-element pressure regulated during the shifting operation and lower than a maximum possible engaging-element pressure.