A hydraulic control apparatus of an automatic transmission having engagement pressure solenoid valves configured to regulate an engagement pressure supplied to a hydraulic servo of a frictional engagement element and to output the engagement pressures from a predetermined number of the engagement pressure solenoid valves to establish respective transmission gear speeds. The hydraulic control apparatus includes a simultaneous engagement signal switch valve configured to be switched from a non-output position where an output of a simultaneous engagement signal pressure is not produced to an output position where an output of the simultaneous engagement signal pressure is produced upon receipt of an input of the engagement pressures by a number larger than the predetermined number of valves; and an original pressure switch valve configured to be switched from a supply position where an original pressure is supplied to the engagement pressure solenoid valves to a blocked position where the original pressure is blocked upon receipt of an input of the simultaneous engagement signal pressure from the simultaneous engagement signal switch valve.