A back-illuminated type semiconductor photodetection element comprising: a silicon substrate which is comprised of a semiconductor of a first conductivity type, which has a first principal surface and a second principal surface opposed to each other, and which has a semiconductor region of a second conductivity type formed on the first principal surface side; and a plurality of transfer electrodes which are provided on the first principal surface of the silicon substrate and which are configured to transfer generated charge, wherein in the silicon substrate, an accumulation layer of the first conductivity type having a higher impurity concentration than the silicon substrate is formed on the second principal surface side and an irregular asperity is formed in a region opposed to at least the semiconductor region of the second conductivity type, in the second principal surface, and wherein the region where the irregular asperity is formed in the second principal surface of the silicon substrate is optically exposed, wherein the second principal surface constitutes a light incident surface and light incident from the second principal surface travels in the silicon substrate, and wherein since light components arriving at the first principal surface travel in various directions because of the diffusion at the asperity, the light components arriving at the first principal surface are highly likely to be totally reflected on the first principal surface and the light components totally reflected on the first principal surface are reflected, scattered, or diffused on the second principal surface whereby a travel distance of the light in the silicon substrate becomes longer. a silicon substrate which is comprised of a semiconductor of a first conductivity type, which has a first principal surface and a second principal surface opposed to each other, and which has a semiconductor region of a second conductivity type formed on the first principal surface side; and a plurality of transfer electrodes which are provided on the first principal surface of the silicon substrate and which are configured to transfer generated charge, wherein in the silicon substrate, an accumulation layer of the first conductivity type having a higher impurity concentration than the silicon substrate is formed on the second principal surface side and an irregular asperity is formed in a region opposed to at least the semiconductor region of the second conductivity type, in the second principal surface, and wherein the region where the irregular asperity is formed in the second principal surface of the silicon substrate is optically exposed, wherein the second principal surface constitutes a light incident surface and light incident from the second principal surface travels in the silicon substrate, and wherein since light components arriving at the first principal surface travel in various directions because of the diffusion at the asperity, the light components arriving at the first principal surface are highly likely to be totally reflected on the first principal surface and the light components totally reflected on the first principal surface are reflected, scattered, or diffused on the second principal surface whereby a travel distance of the light in the silicon substrate becomes longer.