A white balance adjusting apparatus includes a test signal source 13 for generating a black signal for testing and a white signal for testing, a first impedance means 1 for converting currents flowing through three drive transistors for amplifying primary color R, G, B signals into voltages, a second impedance means 5 connected in parallel with the first impedance means, a switch 6 which is selectively closed to flow a current through the second impedance means, a reference voltage source 7 for generating a first reference voltage at the time of performing the cut-off adjustment and a second reference voltage at the time of performing the drive adjustment, a comparator 8 for comparing the levels between the reference voltages of the reference voltage sources and the output voltage converted by the first or second impedance means, and a microcomputer 75 which generates a control signal for adjusting the white balance on the basis of the output signal of the comparator and adjusts the DC level and the AC level of each of the primary colors of R, G, B.