The present invention provides a photoelectric conversion element and a solid-state image sensor, having a simple structure, a wide dynamic range, a high speed and a high sensibility, which includes a principal layer of a first conductivity type, a surface-buried region of a second conductivity type, selectively buried in an upper portion of the principal layer so as to implements a photodiode with the principal layer, a first charge-accumulation region of the second conductivity type, buried in the upper portion of the principal layer configured to accumulate first signal charges transferred from the surface-buried region, generated by the photodiode, and a second charge-accumulation region of the second conductivity type, buried in the principal layer configured to accumulate second signal charges transferred from the surface-buried region, generated by the photodiode, wherein a process including a first period, in which the first signal charges are transferred from the surface-buried region to the first charge-accumulation region, and a second period shorter than the first period, in which the second signal charges are transferred from the surface-buried region to the second charge-accumulation region is repeated multiple times in one frame period.