Because a conventionally known imaging apparatus includes a buffer element for each signal processing circuit, the number of buffer elements increases in proportion to the number of signal processing circuits. The delayed supply of a drive signal within a group of a plurality of signal processing circuits may require the operation timing margin to be set longer. In other words, the operational speed is hard to increase. First buffer circuits connected in series and second buffer circuits connected in parallel with the first buffer circuits are provided, and one second buffer circuit supplies a drive signal to a plurality of signal processing units.