A solid-state imaging device comprising: a back-illuminated semiconductor photodetecting element which has a first principal surface and a second principal surface opposed to each other, which is provided with a photosensitive region on the first principal surface side, and a portion of which corresponding to the photosensitive region is thinned from the second principal surface side while leaving a peripheral portion around the thinned portion; a package which has a third principal surface and a fourth principal surface opposed to each other and in which a housing space opening in the third principal surface and in the fourth principal surface and configured to house the semiconductor photodetecting element is formed; a fiber optic plate which has a light incident end surface and a light exit end surface and which is arranged so that the light exit end surface is opposed to the second principal surface; and a protective member which is fixed to the semiconductor photodetecting element from the first principal surface side and which protects the thinned portion of the semiconductor photodetecting element, wherein a portion on the light incident end surface side of the fiber optic plate projects from the third principal surface to the outside of the package, characterized in that a portion on the light exit end surface side of the fiber optic plate includes a first portion corresponding to the peripheral portion of the semiconductor photodetecting element, and a second portion corresponding to the thinned portion of the semiconductor photodetecting element and projecting more toward the semiconductor photodetecting element than the first portion, wherein a height of a step made between the first portion and the second portion of the fiber optic plate is lower than a height of a step made between the thinned portion and the peripheral portion of the semiconductor photodetecting element, wherein the semiconductor photodetecting element and the fiber optic plate are fixed by a resin being optically transparent to light to be detected, the resin being filled between the light exit end surface and the thinned portion, in a state in which the first portion and the peripheral portion are in contact and in which the second portion and the thinned portion are separated, and wherein the second portion of the fiber optic plate and the thinned portion of the semiconductor photodetecting element are optically coupled through the resin. a back-illuminated semiconductor photodetecting element which has a first principal surface and a second principal surface opposed to each other, which is provided with a photosensitive region on the first principal surface side, and a portion of which corresponding to the photosensitive region is thinned from the second principal surface side while leaving a peripheral portion around the thinned portion; a package which has a third principal surface and a fourth principal surface opposed to each other and in which a housing space opening in the third principal surface and in the fourth principal surface and configured to house the semiconductor photodetecting element is formed; a fiber optic plate which has a light incident end surface and a light exit end surface and which is arranged so that the light exit end surface is opposed to the second principal surface; and a protective member which is fixed to the semiconductor photodetecting element from the first principal surface side and which protects the thinned portion of the semiconductor photodetecting element, wherein a portion on the light incident end surface side of the fiber optic plate projects from the third principal surface to the outside of the package, characterized in that a portion on the light exit end surface side of the fiber optic plate includes a first portion corresponding to the peripheral portion of the semiconductor photodetecting element, and a second portion corresponding to the thinned portion of the semiconductor photodetecting element and projecting more toward the semiconductor photodetecting element than the first portion, wherein a height of a step made between the first portion and the second portion of the fiber optic plate is lower than a height of a step made between the thinned portion and the peripheral portion of the semiconductor photodetecting element, wherein the semiconductor photodetecting element and the fiber optic plate are fixed by a resin being optically transparent to light to be detected, the resin being filled between the light exit end surface and the thinned portion, in a state in which the first portion and the peripheral portion are in contact and in which the second portion and the thinned portion are separated, and wherein the second portion of the fiber optic plate and the thinned portion of the semiconductor photodetecting element are optically coupled through the resin.