An abnormality detecting apparatus, comprising: a synchronous detecting circuit for detecting a synchronous signal from a video signal outputted from a video outputting unit through an output line connected to an input terminal of the abnormality detecting apparatus; and path state judging means (11, 10) for judging whether or not a first direct current signal level obtained from a node of said output line of said video signal is greater than a predetermined first threshold value, whether or not a second direct current signal level obtained from said node of said output line of said video signal is smaller than a predetermined second threshold value, and whether or not said synchronous signal is detected by said synchronous detecting circuit, and determining that said output line of said video signal is in one of a normal state, an open state, a power connected state, and a ground connected state based on the result of the judgments, wherein in said normal state a video signal is present on said output line, in said power connected state said output line is connected to a power line potential, in said open state said output line is disconnected from said abnormality detecting apparatus and in said ground connected state said output line is short-circuited to ground, wherein said judging whether or not said first direct current signal level is greater than said first threshold value generates a first state signal indicative of a power-connected state of said output line, said judging whether or not said second direct current signal level is smaller than said second threshold value generates a second state signal indicative of a ground-connected state of said output line, and said judging whether or not said synchronous signal is detected by said synchronous detecting circuit generates a third state signal, and said path state judging means is operative to represent said states by two signals (CAMIND1, CAMIND2) formed by logical OR combining of said first state signal with a respective of one said second and third state signals. a synchronous detecting circuit for detecting a synchronous signal from a video signal outputted from a video outputting unit through an output line connected to an input terminal of the abnormality detecting apparatus; and path state judging means (11, 10) for judging whether or not a first direct current signal level obtained from a node of said output line of said video signal is greater than a predetermined first threshold value, whether or not a second direct current signal level obtained from said node of said output line of said video signal is smaller than a predetermined second threshold value, and whether or not said synchronous signal is detected by said synchronous detecting circuit, and determining that said output line of said video signal is in one of a normal state, an open state, a power connected state, and a ground connected state based on the result of the judgments, wherein in said normal state a video signal is present on said output line, in said power connected state said output line is connected to a power line potential, in said open state said output line is disconnected from said abnormality detecting apparatus and in said ground connected state said output line is short-circuited to ground, wherein said judging whether or not said first direct current signal level is greater than said first threshold value generates a first state signal indicative of a power-connected state of said output line, said judging whether or not said second direct current signal level is smaller than said second threshold value generates a second state signal indicative of a ground-connected state of said output line, and said judging whether or not said synchronous signal is detected by said synchronous detecting circuit generates a third state signal, and said path state judging means is operative to represent said states by two signals (CAMIND1, CAMIND2) formed by logical OR combining of said first state signal with a respective of one said second and third state signals.