An imaging device that has an image processing function and is capable of a high-speed operation is provided. The imaging device has an additional function such as image processing, and can retain analog data obtained by an image capturing operation in pixels and extract data obtained by multiplying the analog data by a given weight coefficient. In the imaging device, the data is stored in a memory cell and pooling processing of data stored in a plurality of memory cells can be performed. The pixels are provided so as to have a region overlapping with at least one of the memory cells, a pooling processing circuit, and a reading circuit of the pixels; thus, an increase in the area of the imaging device can be inhibited even with an additional function.