Conventional semiconductor devices disadvantageously failed to sufficiently enlarge a dynamic range. A semiconductor device according to an embodiment includes a plurality of registers 21 to 26 that sets a gradient of a ramp signal. In the semiconductor device, the values in the registers 24 to 26 that are reflected in the gradient of the ramp signal are switched at predetermined timings, whereby a ramp signal with a gradient that changes at the predetermined timings is generated, and an analog-to-digital converter uses the ramp signal to convert pixel signals acquired from a pixel area into digital values.