A solid-state imaging device and a camera system are disclosed. The solid-state imaging device includes a pixel unit and a pixel signal readout circuit. The pixel signal readout circuit includes a plurality of comparators disposed to correspond to a pixel column array, and a plurality of counters. Each counter includes a first amplifier, a second amplifier, and a mirror circuit to from a current mirror in parallel with the second amplifier. The first amplifier includes differential transistors, initializing switches connected between gates and collectors of the differential transistors, and first and second capacitors connected to each of the gates of the differential transistors. The second amplifier includes an initializing switch and a third capacitor. The mirror circuit includes a gate input transistor whose gate is inputted with a voltage sampled by the first amplifier or a voltage sampled by the second amplifier.