A solid-state imaging apparatus comprises a plurality of matrix pixels, a reference signal generator for generating a ramp signal, a counter for performing counting according to the ramp signal output, and an AD converter, arranged for each pixel column, for performing AD conversion by comparing a pixel signal from the pixel with the ramp signal. Further, the AD converter includes a comparator to which the pixel signal and the reference signal are input, a storage for storing the AD conversion result, and an slope converter, between the output terminal of the reference signal generator and the input terminal of the comparator, for changing a gradient of the ramp signal, so that the noise overlaid on the ramp signal changes depending on the gradient of the ramp signal. Thus, it is possible to prevent generation of a horizontal-line noise in the ramp signal.