The present invention relates to a solid state image-sensing element and a method of driving same whereby power consumption in cases when low-resolution images are output can be reduced, and to an electronic device. In this solid state image-sensing device, a pixel addition unit outputs a horizontal/perpendicular pixel addition signal obtained by performing addition of pixel signals of a plurality of pixels of different weights in a perpendicular direction, and pixel signals of a plurality of pixels of different weights in a horizontal direction, which have been selected from among a plurality of pixels arranged in a matrix. An AD conversion unit performs AD conversion of the horizontal/perpendicular pixel addition signal output by the pixel addition unit. The present invention can be applied, for example, in a solid state image-sensing element or the like.