An imaging device of the present invention includes a plurality of photosensors arranged in matrix on a light-receiving surface and a readout section for adding up photo signals on the photosensors for external output in each pixel block set on the light-receiving surface. The pixel blocks each consists of N (N≧2) photosensors assembled in an array direction of the matrix and the pixel blocks in even number arrays and those in odd number arrays in the matrix are shifted from each other by half a phase in the array direction. With or without execution of the adding-up operation, it is able to switch a pattern of readout pixels from the imaging device between a grid pattern and a diagonal grid pattern.