A signal processing device, on the basis of signals that control voltages to be applied to pixels, a boundary between a first pixel corresponding to a first signal that applies a first voltage and a second pixel adjacent to the first pixel and corresponding to a second signal that applies a second voltage different from the first voltage at least by a predetermined threshold. The first signal is corrected to a third signal that applies a third voltage higher than the first voltage, and the second signal is corrected to a fourth signal that applies a fourth voltage higher than the second voltage. The second voltage is higher than the first voltage, the fourth voltage is higher than the third voltage, and a potential difference between the first voltage and the third voltage is larger than a potential difference between the second voltage and the fourth voltage.