The present technology relates to a solid-state imaging device and an electronic device that can expand a dynamic range in a pixel having a high-sensitivity pixel and a low-sensitivity pixel. The solid-state imaging device includes a pixel array unit in which a plurality of pixels is arranged in a two-dimensional manner, in which the pixel includes a first photoelectric conversion unit and a second photoelectric conversion unit having lower sensitivity than the first photoelectric conversion unit, and a size of the second photoelectric conversion unit in an optical axis direction in which light enters is smaller than a size of the first photoelectric conversion unit in the optical axis direction. The present technology can be applied to a backside-illumination CMOS image sensor, for example.