PURPOSE: To realize th sure trouble detection of an antiskid controlling circuit by a method wheren a trouble detection signal is outputted when the duration of output, which driving currents of electromagnetic solenoids discriminate as the output of the hydraulic pressure controlling signals produced under the condition that the antiskid controlling circuit in trouble, exceeds the predetermined period of time.

CONSTITUTION: An antiskid controlling circuit 10 repeats the increase, retention and decrease of pressure perskid cycle and issues signals Ev and AV, in which both turn to be "L" level during the period of increase of pressure and only signal EV turns to be "H" level during the period of retention of pressure and both turn to be "H" level during the period of decrease of pressure. Now, when a trouble occurs in the antiskid controlling circuit 10 and the signals EV and AV remain unchanged to be "H" level, the capacitor C1 in a timer circuit 16 is charged through a resistor R2 by means of a "H" level output of a level detector circuit 14 and , when the duration, in which the terminal voltage Vc of the circuit 16 is larger than the reference voltage Vr1, exceeds the set time, a comparator 18 outputs the trouble detection signal. Said signal lights an alarm lamp and as well as interrupts the supply of battery voltages to the electromagnetic solenoids 12a and 12b of hydraulic actuators. In such a manner as mentioned above, the sure trouble detection of the antiskid controlling system is accomplished with a simple circuit.