An electronic device according to various embodiments of the present invention comprises an image sensor and a processor, wherein the image sensor comprises a microlens and a light-receiving sensor pixel capable of converting light having passed through the microlens into an electrical signal, the light-receiving sensor pixel comprises a first floating diffusion area and a second floating diffusion area, the light-receiving sensor pixel is set, as a first area and a second area having different sizes, in accordance with the activation of either the first floating diffusion area or the second floating diffusion area, a signal generated by the light-receiving sensor pixel can be classified and read out as a first signal corresponding to the first area and a second signal corresponding to the second area, and the processor can be set so as to: use the image sensor so as to activate the first floating diffusion area, thereby acquiring a first image of an external object; use the image sensor so as to activate the second floating diffusion area, thereby acquiring a second image of the external object; and synthesize at least a portion of the first image and at least a portion of the second image, thereby generating a third image having a resolution higher than that of the first or second image. Additional various embodiments are possible.