Provided are a photomultiplier and a manufacturing method thereof. The manufacturing method thereof may include forming a mask layer on an active region of a substrate doped with a first conductive type, ion implanting a second conductive type impurity opposite to the first conductive type into the substrate to form a first doped region in the active region under the mask layer and an non-active region exposed from the mask layer, forming a device isolation layer on the non-active region, removing the mask layer, and ion implanting the second conductive type impurity having a concentration higher than that of the first doped region into an upper portion of the first doped region in the active region to form a second doped region shallower than the first doped region.