A hydraulic control apparatus for use with a vehicle's automatic
transmission, the apparatus including a fail-safe switch valve which has
an escape-related output port connected to a drain port of a
transmission-related solenoid valve corresponding to an escape-related
frictional coupling device to establish an escape-related speed step, and
additionally has an escape-related input port to which a hydraulic
pressure is inputted, and a drain port from which a hydraulic fluid is
drained, wherein the fail-safe switch valve is selectively switchable to
a normal communication state thereof in which the escape-related output
port and the drain port are communicated with each other and the
escape-related input port is shut off, and to a fail-related
communication state thereof in which the escape-related output port and
the escape-related input port are communicated with each other, and the
drain port is shut off, so that a hydraulic pressure is supplied from the
escape-related output port of the fail-safe switch valve to the drain
port of the transmission-related solenoid valve corresponding to the
escape-related frictional coupling device.