For testing an A/D converter circuit including a pulse delay circuit constituted by a plurality of cascade-connected delay units, and an encoding circuit configured to count the number of the delay units through which the input pulse signal passes within a predetermined measuring time and to output a digital signal representing the counted number, the method includes the steps of setting the A/D converter circuit in a test mode where the measuring time is set at a short test-use sampling period, applying the input pulse signal to each of serial delay blocks each of which is constituted by a predetermined number of the delay units, and determining good and bad of the A/D converter circuit on the basis of digital signals outputted from the encoding circuit representing the numbers of the delay units through which the input pulse signal has passed within each of the serial delay blocks.